What I'd like to see in most IDEs in 2021 is perfomance improvements. It's a chore to scroll through in most of the mainstream IDEs (VS, VSCode, IntelliJ, etc.) when the loaded project is large.
Arguments can be made to have smaller files, projects yes. But, in my experience at all the large corps this isn't as easy since legacy code exists in large swathes.
Smooth scrolling, quick finds, indexes would be godsend right about now.
Not cheap, but if you are dealing with large code bases, it is definitely worth it to invest in a powerful workstation.
While not the most powerful, i have found few codebases I couldn't navigate smoothly with my 6 core i7, with 64GB of ram and dual 500gb nvme drives running in raid 0.