However, I actually need to learn Croatian, a Slavic language. This is extremely difficult for me and I make hardly any progress. The vocabulary is so different from everything else I know, I just can't remember the words. The grammar is quite challenging as well.
E.g. a curious thing I noticed is the frequent complaint about Latin being very hard to learn because of the seven grammatical cases, three genders and morphology -- words just don't stay the same. As native Russian speaker I find these things absolutely normal and easy to understand, but I can image this must be a nightmare after English.
Slavic languages you mention are very curious in how different yet how similar they all are. One of the most impressive thing I saw with respect to learning languages is the Interslavic language [1]. Apparently if you speak any of Slavic languages you can understand it quite well, even though you usually are completely lost with most of the other Slavic languages. You still need to learn to speak it, but the fact that you understand foreigners with zero training just blows my mind. Feels like you awakened the memory of your ancestors of something.
The experience is weird - when I first went to Ukraine I couldn't understand almost anything. After a few days it suddenly "clicked" and I realized how the most common sounds and word endings relate between Polish and Ukrainian - and since that moment I basically got all the words with the same roots for free (which is like half the language). It also gave me Belarusian as a side effect :)
Of course it's not actual language speaking, I'm just understanding every other word and connecting the dots.
With Slovak it was even quicker, but somehow it hasn't given me Czech - their pronuciation is just too weird, despite the fact it's almost the same in writing :).
I'm not sure Interslavic provides much value. For me it's basically Slovak, so if you come from East Slavic language you'd probably get the same benefit spending that time learning some Slovak, and you'd then know some actual language instead of an artificial one.
This comes from limited first-hand experience and more extensive second-hand cross-generational experience. Take it as you will.
But if there is no exposure, its becomes visible how grammar is very similar, but most words are just a bit different (very few are completely different), and pronunciation varies so much across whole region (even within given country) that its not easy or even possible to understand each other out of blue, without prior exposure.
I got some exposure to Polish TV during 80s, since commies couldn't put together more than 2-3 channels on TV and those were anyway pretty bland. I can cca understand it, but can't say a single sentence well enough. If I read polish text, I have to read it loud in my head and then I grok it easily, otherwise too much 'cz', 'w', words are too long etc and I lose meaning very quickly.
But in general Polish is a bit further away from either Slovak or Czech languages. We were and still are literal brothers (CZ and SK), extremely similar in so many regards, still see no good rational reason why we split up (of course I know real reasons, but those are nasty as are the people responsible for the split).
A story I've heard first hand is that after the program, department staff can discuss diplomacy in the target language, but struggled to order a coffee!
Absolutely! The way they teach foreign languages in school is insane. "OK, you know 20 words and can't say a thing, now it's time to learn past tense".
Even if it's not the tenses, still schools typically put a lot of focus on grammar and order of words but not even nearly enough into speaking. I have an suspicion that these corses are modelled after native-language programs which rightfully focus on grammar because everyone knows how to speak already. But starting from it is madness.
Our brains are all extremely capable of moving a few words so we can understand things in context. When speaking Dutch, I'm spending a lot of time thinking about a verb, then attempting to string it together into something comprehensible.
What I also found to be almost universally true, is that if you are learning a less "popular" language (like Dutch or Ukrainian), just actually give a shit enough to learn more than "yes/no/please/thank you/my name is" will garner you a lot of good will from native speakers. Some countries get so many tourists that hearing the same 10 words butchered over and over and over and over and over again eventually starts to wear down on locals, making them jaded.
When you can walk into a room and somewhat confidently hold your ground, you become interesting and a novelty that people want to interact with. I went to a block party last weekend and spoke to most of the people there throughout the evening. Sure, everyone knew I was "foreign" and occasionally I had to ask someone to repeat something or re-word it, but that's a minor complaint for them considering the other option is to speak back to me in a language they don't have as good of control over. Despite popular belief, even in many "English friendly" countries, the normal citizens aren't actually that comfortable speaking unless they work in an environment that demands they speak English every day. This goes doubly so for older people. My next door neighbor is about 75 years old and speaks English pretty well (worked at Philips for 20+ years), but the _quality_ of our conversations went up 3x when I could understand enough Dutch for them to speak naturally to me.
All that to say, I agree with you! Vocabulary and basic grammar to get you started and then after that it's all about learning words and practice practice practice.
You can get away with a lot in Dutch and especially Flemish Dutch though, because the local dialects are so strong (for being a relatively small area). Unless you look exotic, people don't always immediately pick you out as a non-native speaker.
Given that the state language is Ukrainian, and its overall dominance in media and culture -- there's no way this statement could possibly make sense.
Everybody speaks it in Ukraine.
This gets repeated a lot, but it's just not true. It's true that virtually everyone has some working comprehension of Russian because of earlier Soviet influences, and because the two languages are so similar (and in many parts of the country, the "Ukrainian" that is spoken is highly Surzhyk-influenced).
But realistically only about 70-80 percent of the population speak Russian fluently and comfortably. Given a choice, the vast majority would clearly prefer to speak Ukrainian (and many people have been switching voluntarily as a matter of preference since 2014; the government's mildly coercive efforts having nothing to do with this, really).
Even at our university in Ukraine, Russian was the main language amongst foreign students.
Probably because it's the only one among the two that they were able to study before coming there (and because they saw Russian as being more useful in other countries, as you say).
And even so, this applies only to certain universities in certain cities.
Then you haven't traveled broadly in Ukraine. And more importantly you're missing the point. The vast majority do speak and understand a reasonable amount of Russian (hence they will almost never object when you use it with them; they get that you're a foreigner and are doing the best you can) -- but they don't speak it fluently and comfortably, and it's not their preferred language in everyday use.
Only the elderly people have sometimes a mixed slang
It's more prevalent among the older set of course, but still this is just not true across the board. Surzhyk (or less pejoratively: Russian borrowings/breakings) are everywhere, though they are often subtle and it may take some training to detect them.
Part of the problem is that there are no well-defined boundaries (and there's only a barely defined notion of what constitutes "standard Ukrainian"). They're literally still in the process of cleaning up the nation's preeminent (and clearly Soviet-, if not exactly Surzhyk-influenced) dictionary.
There are some hardcore nationalists connected to Bandera (pro nazi group) that refuse to speak Russian
Now you're getting into pure BS territory.
This is obviously something you've read or something you've heard said a lot, but not something you know from direct observation.
Anecdotally, I know that I can understand people speaking English with what a school teacher would consider atrocious grammar, as long as the words are pronounced close enough to be recognizable.