I use telekinesis to speed up my Pindil runs by zapping the portal to reduce walk time. I noticed that I can only target the portal if I’m closer than the tree about a half screen away.
In the old game telekinesis worked on the whole screen and beyond. The skill should have no problem working in the wider resolution of d2r because in the original game if you used resolution “mods” the skill still worked way beyond the max d2r resolution.
I suspect the nerf was put in place when ultra wide was still a potential option to prevent those people from getting an advantage and Blizzard just over compensated by restricting its range to what can be seen in legacy mode.