Do you have some examples? I've used IntelliJ or variants of it (Clion primarily in more recent years) since ~2004 and rarely had any issues, but it's possible I'm missing some obvious things here.
Wow, never had this, I use IntelliJ (for java) many hours everyday with 2x4k@60Hz screens (both running with hidpi scaling so even more pixels than 2x4k) and it’s always running smoothly. Running MBP 16”.
Interesting - my own setup is the built-in 15" high DPI display, an LG 5k display and a Dell 49" ultrawide with a low DPI. I've not really experienced this. Probably scaling mode or similar.