Familiars are really exploitable. The Imp warlocks get can invis stealth into a group of enemies, attack one, fly away without provoking opportunity attacks, and then hide as a bonus action. Then next turn they can invis and stealth back in, and the next turn start the whole thing over again. After the familiar hides the AI dont look for it or anything. Im able to send my familiar across the map alone and solo encounters with no cost since it doesnt use a spell slot.
This could be solved by not letting the familiar hide as a bonus action. While the process might sound tedious, it's pretty easy once you get the hang of it and I was even able to solo the four level four gnolls outside the blighted village with JUST the familiar.
Even if you mess up and the familiar dies, you can just try again for free. The only case you wouldn't be able to do this is in an enclosed environment or there being so many enemies there is no place you can feasible go to hide even with flight and movement.
This is yet another example of how what would be considered a rather small change to someone not knowing D&D5 can snowball into something really broken.
Rogues (and other subclasses exceptions) should be the only ones featuring hide/dash/disengagement as a bonus action.
Opening up those things to everyone makes the game broken and it doesn't feel like a D&D5 based game should.