Who cares about 300Mb, where is that going to move the needle for you? And if the alternative is a memory-unsafe language then 300Mb is a price more than worth paying. Likewise if the alternative is the app never getting started, or being single-platform-only, because the available build systems suck too bad.

There ought to be a short one-liner that anyone can run to get easily installable "binaries" for their PyQt app for all major platforms. But there isn't, you have to dig up some blog post with 3 config files and a 10 argument incantation and follow it (and every blog post has a different one) when you just wanted to spend 10 minutes writing some code to solve your problem (which is how every good program gets started). So we're stuck with Electron.