Apparently the UFC was trying to make Gaethje vs Poirier II be a TUF thing and its only because Poirier turned it down we got Fiziev vs Gaethje. Arman Tsarukyan vs Damir Ismagulov made no sense and both guys had the potential to be title contenders but nobody else was willing to fight them. Islam Makhachev, I can't say was "avoided" entirely because Makhachev pulled out vs Prazeres, Trinaldo and RDA but Makhachev also had Beneil and RDA pull out against him too but one thing is clear Michael Chandler was afraid of him, Hooker wanted badly to avoid him and Poirier wanted nothing to do with him.
We are going to see a trend of Russian, Caucasian and Central Asian fighters getting avoided in the UFC, not because they are inherently better but they are very good and have a style that a lot of fighters simply cannot deal with. Beyond, they don't get the same kind of rub from the western audience, they aren't often as marketable or popular so promotions don't want them dominating and ranked guys feel like they're a high risk / low reward situation. It sucks but this is quickly becoming the norm.