The jokes were mostly about startup time for the JVM (only happens once as when its in RAM it stays there and the loading time doesn't repeat for the next java program you run). It was also a lot more notable in the 90s when java was a browser plugin to run applets and browsers were single threaded (so the browser froze for a few seconds while the JVM loaded).

I think it's been out of date for a long time with modern computers having much more RAM and speedy SSDs (and also JVM optimizations). For actual run time performance once its loaded the JVM has had great performance in the early 00s already and improved since. And for server side it was never an issue as you don't restart the server very often (so the JVM is always already loaded).