You actually can, you have to stand exactly infront of the entrance.

Edit : If i remember correctly, then this is the spot where you should enter.


(Sorry for a bad picture, i am on my tablet)

Please let me know if it worked.

^ Correct you have to be on a spot little more to the west to get in, however it is worth reporting since it's quite annoying.
To answer your question "Why would you move the cave entrance?", well that was quite a lot of people got stuck behind the cave entrance which means they couldn't get out, not to forget that it's around wildy level 57 there which means they couldn't teleport out either!

Next update will let you walk to the correct spot automatically. Thanks.