I wasn't aware that they'd completely stupified familiars in 5e. Is there anything they didn't completely dumb down?
Its less they dumbed them down and more they buffed them to an extreme.
In 4e they were more or less a passive that provided a benefit so arguably there they got dumbed down compared to older editions.
In 5e, however, they became a lowlevel summon, not great for direct attack but allowing the caster to deliver touch based spells, which is very very strong considering if you somehow get one for your cleric, they became great for scouting partly because their death wasn't much of a penalty, and they could be different kinds of animals such as a snake.
Warlocks they are are buffed even more because they can be a small list of other creatures instead of a low cr animal, like an Imp or Pseudodragon, which is stronger in 5e than it was in older editions, and can gain certain invocation bonuses like being able to attack on a player's minor action instead of standard and allowing the caster to regain hitpoints.
It is less that they were dumbed down and more they are mechanically very different and have a lot more happening with them than before.
Arguably, it is BG3 that dumbs them down because now they have their own turns and have few of the benefits/complications they had before.
