Increase skill cap side for survivor.
This isn't going to be some outlandish idea about making things impossibly hard and requiring a high level skill cap to learn. It is an idea i present as the games main objective in the game is rather stale.
The idea is to basically give an increasing difficulty to the size of skill checks as the game progresses. Nothing extreme and not like old ruin that required just the great skill check zone to progress.
With 7 generators left on map skill checks remain unchanged. (5 gens remaining)
With 6 generators left on map skill checks "good" skill check zone is decreased 5%.
With 5 generators left on map skill checks "good" skill check zone is decreased an additional 5%.
Basically repeat that skill cap for "good" skill checks progressively gets smaller (not in visual size but total length of the acceptable skill check) to a total of 20~25% smaller.
This, in my opinion, will bring back a bit of a thrill to the survivor side. It isn't extremely overbearing but as the game progresses skill checks being smaller means more focus is required.