Both in terms of their damage, and their AI, the turrets used to be a much bigger threat, and tower-dives were much more risky. I personally preferred the old turrets, and feel as if the new ones basically don't matter. They're only there to make sure you're not taking turrets without minions.
That's a loaded question that's begging the answer, but turrets right now are too weak anyways.
In my opinion, turrets are way too weak. I'd like them to have stronger defenses - at least early game, or do more damage per hit (or even hit more frequently). I can't remember the last time that an unsuccessful tower dive lead to the diver dying.
I only started playing in early season 6, so I don't remember "the good old days", but turrets certainly seem quite weak right now. When I'm playing top lane, as early as level 3-4 there are toplaners and junglers who can dive with little to no fear. That doesn't seem healthy for the game.
