dBeaver is written in Java, but it feels very lightweight. I'm running it on a Linux desktop I've been using since 2014. It's also cross platform so I run it at work on a Windows laptop.
Written correctly, Java can be both very fast and light. Eclipse IDE, written with Java consumes less resources than a comparable Atom/VSCode instance, with more features enabled.
Electron apps are not exactly lightweight either; it is about first time that someone uses them in an argument.
Query Analyzer was written with win32-api. No electron, no java, no c#, nothing (thought it might used MFC, not sure about that). It was snappier on Pentium 3 than Dbeaver is on M1 or Threadripper. Existence of slow molasses like Electron won't change that.
I didn't use DBEaver, but written some Java and using Eclipse for 20 years.
Java's UI libraries are extremely prone to wrong initialization. If you skew from the reference guide's implementation, Java's libraries try to mend the problems themselves, but this adds observable latency to the UI.
Of course, Java is never as fast as natively compiled language, but asymptotically approach to that speed and come pretty close. The funny thing is, some of the today's native applications are both heavier and less responsive w.r.t. their Java counterparts. This is because we tend to add loads of dependencies which aims to simplify development in said language, but that price is always paid at the end. Either once by the developer, or repeatedly by the user.
