In case this somehow isn't mere parody...

"Trash" doesn't have to be "just trash" though. In other MMOs, I've had certain pulls of "trash" mobs that were more engaging that any XIV dungeon boss fight (granted, not a high bar) or even the majority of its normal raids.

The issue is that XIV trash mobs in particular will almost never have anything but auto-attacks, the occasional auto-attack-but-slightly-stronger-and-given-a-name, and well-marked delayed AoEs.

...At that point, yes, of course they're going to be uninteresting, just as would a boss that does nothing but autos and the occasional telegraphed AoE with plenty of time to avoid.

The simple solution then, is to give them more to work with. Beyond that, though, they also need to adjust player behavior over the fight in some way, such as by forcing out prepositioning, target-focusing, specific counter-events (such as interrupts, stuns, or movement skills), etc.