Flutter has had its performance issues in the past (like scrolling on iOS, and shader performance issues), and I recall someone saying that Flutter apps lag on an Android phone that is still able to play the latest games decently.
However, things are looking up with the change from Skia to Impeller and I'm hopeful about the future.
Way, way, way overrated, the "write a brand new rendering engine to eliminate all runtime shader creation" leaves me much more confident speaking strongly in public.
Flutter in 2020 could render a complicated UI (new Google Assistant UI with glowing effect) on a 2015 $200 Android, and there was simply no way to do the same in Android proper. (Source: built Android version at Google and built Flutter version after for no particular reason, side project to teach myself Flutter)
People tend to remember Flutter anecdotes that correlate well with previous xplatform framework fundamental issues, but in Flutter's case, they're not fundamental, they're more "holding it wrong" / "could use better docs"
That being said it's probably a year or two away from me being brave enough to post that on an HN article (safe here, because articles old, weekend, and not directly related to Flutter).
Nice to see we're mostly in agreement, since (as I said in my previous comment) I'm hopeful for Flutter's future. The team writing their own rendering engine is unexpected and I hope to see the same engine used in other projects too.
However, things are looking up with the change from Skia to Impeller and I'm hopeful about the future.