Problem is split route don't work in a DF format, the ability to have an easier time queuing for dungeons of course comes with the sacrifice of path progression.

Think about how "fun" it would be to be ina group, people leave cause group went right, person gets kicked for going left, all 4 want to go in different directions, it's just chaos that you can't really subside through DF and it's also why they are introducing sky islands because they are fully aware how mechanical the dungeon process is.

However the reason why the dungeon process is always the same is because people will always choose the quickest path to progression, if they were to make dungeons more dynamic it would be less "these dungeons are all the same" and more "I only do y dungeon cause it's faster than x". That's another reason dungeons have to remain the same because changing them ever so slightly may alter the time it takes to complete each dungeon and even "small" changes might be enough to make one dungeon less worthwhile than the other.