There was a thread here (found it) just the other day where Polish people specifically said "we don't use those accented characters any more because it's too hard on mobile and we don't need to" (heavy paraphrasing mine).
I see a Slovenian person claiming that, I think, but no Poles.
Also, often those "accents" are different sounds. Ș in Romanian is sh, ț is ts, ă is uh, â is a sound which is not present in English (at least not explicitly). You can get rid of them but there's definitely ambiguity. Even French has é which sounds nothing like the French e.
https://news.ycombinator.com/item?id=18688619