The frustration goes away with time. It's always going to be slightly more friction and that's worse when tired, etc, but the cost becomes less.

As someone who's done a second language to fluency past 30 years old, the largest hurdle IMO is the inverse frequency curve for words (not sure what the real term is).

But basically, the most common (and therefore most easy to pick up and learn) words carry the least amount of meaning. A, The, Where, Why, etc..

The most meaning-dense words are the least common, and therefore you learn them much slower when consuming native media.

It gets to the point where, if you learn a quarter of all the words in a language, you can read every word of most sentences except for one or two, and those 1-2 words carry all the meaning.

It's incredibly frustrating and the only way through is grinding vocabulary lists, as far as I know.

English native -> Norwegian C1 in ~ 5 years. The back half of any language learning is brutal, IMO. I had a huge dip where I stopped being able to absorb vocabulary via osmosis and consuming media, and just had to grind. But maybe that's just me.