Why do talent trees need to be homogenised? Of course they're built by different teams; I would not want the mage class design team working on the druid talent tree.
Interestingly, the three classes with baseline interrupts are the same classes that have had them since Vanilla WoW. They're core, intrinsic, key abilities that have existed for close to 18 years at this point. I would argue that shamans should be included in that list since Earth Shock also dates back to Classic, but I understand them removing it from their baseline to bring it inline with other healers. Otherwise, the classes without baseline interrupts are those that have historically not had them for every spec or did not have them as core functions. E.g. priests, druids, paladins, monks have not usually had access to an interrupt while healing. Warlocks needed a specific demon out for their interrupt most of the game's history.
Furthermore, I'd argue that the talent choices are indicative of a larger organisational effort. They specifically made sure that three classes, 1/4 of the total classes, always have an interrupt. You're doing a raid with a key interrupt ability? You just make sure you have one of these three and you're set. Same with dungeons.
Spreading out utility and power is a good thing; it leads to classes with depth and niche instead of general breadth.