Compile times are my biggest struggle, too. I'm vibecoding Bevy with parallel agents, and the bottleneck is often compiling the changes on my 7950X, not getting Codex to write them.

As far as file sizes go, I'd be really interested in how a Rust compiler that didn't monomorphize so much would perform. Right now you have to modify the source code to write polymorphic generic functions, but it doesn't strictly have to be that way (at least as far as I can see).

I wouldn't use Bevy for a web only game either, especially while it's still single threaded on WASM.

Bevy website has some tips for improving compile times, have you tried them out?