To be honest it's not really hard. In my first few days in PF, I've already gotten into the end a few times, though I've not had fly. It works perfectly fine even without rtpend
But how many nonlooted end cities have you found? Getting from island to island also isn't easy without /fly, I'm not saying that it can't be done, but it would be easier with a command.
I think you are forgetting that the /rtp randomly teleports you to a location. so if u do /rtpend it would randomly teleport you to a location in the end. that means it could also bug out and teleport you to a random location above no blocks because that part of the end hasn't been generated yet. which would cause people issues and make some people never use the command.
Actually no I'm not forgetting that, part of the rtp command is it randomly teleports you to a safe location, rtpend does the same thing, so you don't send anyone into the void. You materialize on blocks .
Sadly this won't be coming as it could turn to OP, maybe if there were cooldowns however owner decided no. Thank you for suggesting! Yours sincerely, Manager b0ii.