Personally using Flutter or not is not a question about whether it is good or not.
It is a choice between UX and resources.
If you are targeting a social APP with millions of users, a slight improvement on UX and performance would leads to huge impact on $$$. So go native.
If UX doesn't matter that much, or you don't have enough resources, sure, use Flutter, or react native, it doesn't matter.
Or even worse, if web is just acceptable, then go web.