Use the archived link to RoT wiki. That one had all the hidden ubers marked. Worldbosses arent on there yet.
To tell them apart: worldbosses spawn in any difficulty and dont have their own specific zone. Hidden ubers have their own little zone, where portals are blocked, and spawn in hell only.
Sounds like you arent ready yet for ubers. Once fully geared, itll take about 0.5-1 min to kill them.
They can, but imagine the negative backlash from the hardcore d2 community. It’s those people who make the most noise. So they decided to not change anything at all. (Heck, every once in a while some of those purists try RoT and start ranting in the discord how bad of a remake it is and leave again).