I'm not that fussed about people using UI mods that simply change the appearance of existing information, but when they start making modifications that are providing more information then the game does normally it starts to feel a bit uncomfortable.

Granted, a lot of this stuff could be argued to be QoL that should be in the game to begin with (IE, displaying only important debuffs from other players like Trick Attack and Chain Strategem, displaying your debuffs on enemies without needing to target them for DoT management purposes, etc), but it's still an advantage.

When it comes third party program usage in general, there has been a definite uptick in that regard; partly due to the creation of various add-on platforms that make them far more accessible then they were originally as people can now easily browse/install them from an exhaustive list of different plug-ins ranging from harmless like the BRD macro player to straight-up cheating like bots for virtually every aspect of the game you can think of.