As of Xcode 9 this became a breaking feature (at least for me). Xcode had a hard time scrolling through the massive list, so searching online found a few solutions, and I just compiled them together here:
1) Remove yourself from iOS teams you no longer work on.
As far as I can tell this is a recent addition, as before you had to ask the team admin to remove you.
2) Remove the profiles from your machine (might as well nuke them all).
The path to do this is here (credit goes to Alex from the Houston iPhone Developer UG):
3) Remove all the simulators you no longer need, I'd say remove all of them then reinstall the ones you want.
In Xcode go Window -> Devices and Simulators
Unfortunately there's no "Delete All" or select all feature. You'll have to manually delete them 1 at a time.
Or if you're extremely brave (I'm not) you can try this in the command line:
Credit goes to Joao from the Houston iPhone Developers UG:
I totally do not know if this will work, you've been warned :)
4) Add back the simulators along with their versions of iOS you want.
In the same Devices and Simulators page in Xcode at the bottom there is an add button:
Now you should have a nice clean list of the simulators and the iOS versions to choose from:
(before it was about 10-20 simulators of the same type with just a certificate number next to it)