Flutter is a joke on the web, and it consumes as much as Electron, sometimes worse, on a desktop.
I'm not sure if the web render engine has gotten better since then, and am too lazy to look up the links rn, but threads should be easy to find using HN search.
Still seems like a common source language + GUI toolkit that targets the web platform and various native platforms (mainly Android, iOS, macOS, Windows, and desktop Linux of course) without significant overhead has not been achieved yet. And it's questionable whether it's possible, given the special requirements (and capabilities) of the web platform and the different native platform.
For Flutter web, yes as it's canvas based it doesn't have all the same web features but generally for crud apps it doesn't much matter, especially if it's near zero effort taking your Flutter mobile and desktop app and putting it on the web. With the new impeller renderer and Wasm improvements it has gotten quite faster too.
Hopefully the desktop story is going improve as Canonical is now leading the Flutter desktop side.
Google lost the opportunity to actually make it take off, had they replaced the Java stack with Dart, instead of staying in the Java world and adopt Kotlin.
However the Android team was never a great supporter from Dart in first place, hence why you won't find anything Dart on https://developer.android.com.
Kubernetes was originally written in Java, and Docker in Python, it was thanks to early Go advocacy, that those projects got rewritten in Go, and then they got lucky.
Just like the download server rewrite into Go, that was done by someone from Go team, as part of their advocacy.
Check how many public projects does Google do, outside anything related to CNCF project landscape.
Performance is very fast as it's all natively AOT compiled machine code without any web views like Electron.