A major difference is that as far as I can tell flutter is long term meant to be the main way to write native Android apps.
Flutter on web has this kind of problem due to how they handle text differently then a HTML does and HTML provides no way to customize it to the way they need it.
Flutter on Android, iOs, Linux, etc. won't have this problem.
Most modern UI's render with a graphics API like OpenGl (ES), Firefox does so for HTML.
Given that the underlying Android system heavily relies on the JVM, the heavy emphasis on Kotlin support and the 3rd party nature of Flutter (you need to build bridges to use it) it is simply yet another x-platform tool to build mobile applications.
Currently yes, but I believe long term this will change.
And they aren't putting all of their eggs in the same basket as Jetpack Compose is now in active development and will, once ready, rival SwiftUI in functionality and power.
I hope there will be flexibility and support for both in the future. Flutter has its positives and negatives as everything else. Same can be said about native development.
Otherwise there's no point in choosing Flutter to develop for the web.
Okay, so you can't reuse UI components, surely you can reuse the Dart code that makes up the guts of the webapp? And, sure, you could, but why would you when you can spend maybe 10 minutes to translate it to native JS (the two languages are practically identical) and ship it without the Flutter Web dependency?
I actually feel like it'd be easier for me to convert some of my Flutter components into React ones, than to try and learn Flutter Web and set up its whole toolchain. I think it's a cool idea, but it's not meant for widespread use (speculation): it's meant specifically for Google's Fuchsia, where they are probably planning on shipping Web applications pretending to be native desktop apps along with the full Chrome experience much like they did for Chromebook.