It's probably due to optimizations in high level code rather than the 32/64-bit aspect, but I'm just guessing. (To get that level of slowness you really have to fuck up at a higher level.)
VS seems to be a WPF app nowadays, so I assume the UI is written in C#.
It was a surprisingly bad experience - weirdly slow even on a high performance PC and so much clutter by default.
Tried out VS 2022 just now. First impressions are better.