So it had performance issues when you last used it a god couple of years ago ......
I don't have an issue with the LR Classic UI. I never liked LR or Photoshop to start with. I got used to them. Having got used to them I don't like change. I have managed to tolerate one change to another tool - Capture One - which I found just as annoying as LR when I started out ..... but I got used to it.
I hate using a phone or iPad for image processing. But I see the iPad pro seems to be competing well with the likes of the Macbook Air as a convenient end user device these days - for many people.
And this sort of demonstrates Adobe's problem as a major incumbent supplier. They have luddites like me to keep happy and those who want newer stuff and UI like you to keep happy. I think the numbers of us luddites must be quite high because I don't think it was Adobe's intent to keep LR Classic going this long.