I honestly don't mind OP, as long as it's with half health.
Ever since they changed the protection level to prot 4, I can easily kill anyone in a matter of seconds. Matches lasting forever won't really happen much as you can get an enderpearl if they camp their island. If they camp mid however, you'll be in quite the situation.
But I can definitely see some games lasting ages because of OP mode.
But you have to look at it from Cube's POV. If a player has a rank & wants to vote against someone else voting for OP, they can do it because of their rank.
If you want to vote against someone voting OP, you'll need a rank. Going to the board where you can vote for OP is pretty much always going to have OP or hardcore (as players can vote there)
Those boards will be targeted by OP-preferring players. This'll result in the NORMAL guaranteed board, and the OP/HARDCORE guaranteed board. Which again, removes the purpose of a rank in some cases.