I had not given this any thought. I just assumed D2R was the latest version and that everyone was playing it.
Now that you mentioned it I looked up the differences. Here they give a whole list (most are QoL things): https://www.reddit.com/r/diablo2/comments/1bkvl8g/diablo_2_lod_vs_diablo_2_resurrected/

I just got a bit of FG so now I can actually participate!