>Don't FATE grind it's inefficient / there are other options etc.

It's a part of the game designed for any player at that level to do. If they want to actually be on a FATE grind train, they can and should be allowed to enjoy it. Just because it's not efficient or they have other options does not mean that they should not be allowed to fully enjoy the content designed for their level.

One of the best solutions is for ATMA parties to also allow the players who are enjoying the content provided to them to join their groups. The problem is when you have a map that has like lvl 15 fates through mid lvl 40s and if groups are dicks about it since their low level party members wouldn't help contribute in the higher level FATEs.