I also was a professional java dev, and also had to use spring boot in most corporate environments.

I don't wanna knock anyone's re-write, because I know how difficult it is to dissuade someone when they're excited about a project. But to me, starting a new project or doing a rewrite, is the best opportunity to learn a newer, better language. We taught ourself Rust by coding lemmy, and I recently learned Kotlin / jetpack compose because I wanted to learn android development. Learning new languages is not an issue for most programmers; we have to learn new frameworks and languages every year or so if we want to keep up.

This is potentially hundreds of hours of wasted time that could be spent on other things. Even if someone absolutely hates Rust and doesn't want to contribute to the massive amount of open issues on Lemmy, there are still a lot of front-ends that could use more contributors.