I'm a flutter developer, I'm relatively satisfied with it. There is a few missing things that could get me to switch if your framework does them better.

First, 3d rendering. I'm already using Flutter to back a 2d game and I'm not alone. A cross-platform framework has a lot of appeal for game devs who'd like to release everywhere and are okay sacrificing a little performance for it. Flutter has some 3d rendering support, but it doesn't work on web.

Bundle size is a pain point for flutter, an improvement here could be great.

Web is an important platform. SEO still matters. Cross-platform frameworks tend to struggle here. How does this do?