Finland is still in many ways a very conservative society.
In everyday life speaking Finnish will be beneficial, for obvious reasons. I've been here a few years now, having moved from Scotland. Using English I've been able to get my brain scanned, buy a couple of flats, deal with daycare (I became a parent after moving here), and most bureaucracy.
Finnish is indeed hard to learn, but even getting the basics down will make your life easier and better.
There's also regions along the coast where a sizable portion, or even the majority of people, are Swedish speaking[1] (and bilingual to various degrees). Swedish is an official language, and if you want to be a pain in the ass to the 95% of the population that doesn't speak Swedish apart from the mandatory school courses, you are entitled by law to get service in Swedish.
Working only in English is obviously harder, but if you want to live here, don't let that stop you.
I speak from experience. I’ve lived in a central Europe country where I cannot speak anything and it was annoying outside work; I felt like an idiot most of the time. Now I’m living in a country I can speak the language and I can interact with people, do complex things alone (moving home), and it’s way more nice to live like that.
I think there are a few exceptions in Europe, e.g The Netherlands.
There's just a big jump from simple things that will get you by to actual fluency.
In my experience Finnish is not required for jobs at 95%+ of product companies, only consultancies and even there there are exceptions.
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It is very, VERY common in both IT and education sectors to hire people who speak no Finnish.
I've personally hired half-a-dozen English-speakers who do not speak any Finnish.
Our company (mobile gaming) consists of ~10% non-Finnish speakers, all of whom are very happy here. Almost ALL Finns (incl. our cleaning lady) speak good English.
My previous company (hardware) had roughly ~10% of non-Finnish speakers as well.
Both universities here have hundreds of non-Finnish speakers. The game education program in Oulu University of Applied Sciences (Oulu GameLAB) is being run by (a super smart) Romanian who does not speak a word of Finnish.
The local Nokia office has hundreds of people from abroad.
There's an active Chinese community of couple of hundred people, most of whom do not speak Finnish.