I agree, I don't get the massive push for keyboard-only usage and terminal applications, I have a mouse and it's good for pointing at things and clicking, I don't want to stop using it! The keyboard is good for certain things, some shortcuts are nice, but too much become a hassle. There's a reason I'm not using Vim.
My wrists are the reason.
More than 10 years ago they started to hurt, so I became a left handed mouse user at work. A couple of years ago I started using a vertical mouse. If I could leave them in a mostly static position I would.
There's the added fact that I'm much faster with keyboard only and I can perform the actions without effort once I have them ingrained. Mouse is slower and even when you know where to go it needs more of your brain.
Having said this I'm perfectly ok with people preferring mouse, I'm just starting the reasons for my preferences. Not that they matter, I'm not using JetBrains.
If you haven't you should try a thumb trackball mouse like the Logitech MX Ergo, just move your thumb to move the cursor, significantly easier on the wrist. I've been using it as my only mouse for years.
I came to IDEA from Emacs and I used mouse there too but weirdly enough it feels worse in IDEA