My experience with React has been different hence commenting here. That is just not true. I have used react with nextjs in the past but moved to remix. Moving to a new framework requires you to learn it, quite similar to learning a new language but it is much better than manually creating webpack loaders. I had a decent experience with nextjs but my experience with remix has been better.
I used Spring Boot at work and I have worked with backend libraries like Express(JS), Flask(Python), Gin(go) all the experiences have been much better than using Spring Boot. Java takes too long to compile, dependecy injection in Spring just seems to take forever, and overall Java is very very verbose. Just to create a stupid API, you have to create a new class for request, one for response, controller, service. I can do it if I am paid for it but using that for side projects, a big NO.