If you use gargantuan Java frameworks, you'll use a lot of RAM. Just don't do that. With Spring Boot and similar frameworks, the RAM usage is really just very modest. I'll give you startup times, since I am not a believer in Quarkus and Graal. And I wouldn't use Java for a serverless function that needs to spin up and respond quickly. But for a typical (blue/green-deployed) application in my world, startup time is still only a few seconds, which is fine for many applications. And I am not settling for "fine", just saying that the startup time isn't a big consideration, against a lot of things the Java (or Spring, in my case) ecosystem offers me.
You are probably right. It's one of those things where I've not seen a need to jump aboard. I'm still being fearful of reflection going to break on me. Probably irrational fear, but fed by me not understanding how it wouldn't break. Which I should study up on. Which I don't, since I don't have the need. And here I am ... vicious circle.
To be fair there is the new Kotlin based wiring API which avoids that with the caveat you need to instantiate everything manually etc. Which is probably a decent tradeoff for some folks.