Are expansions getting worse with each Sims game?

Yes.
Apartments in 4 don't even come close to the game play that came with apartments in 2.
Sulani can't compare to Isla Paradisio.
The "quests" in sims 4 vacation worlds don't compare nearly to those of WA in 3, or even the game play of 2. And because the worlds are all connected, we are restricted on being able to designate any lot in ANY world as a vacation retreat.
Seems to me every expansion pack for Sims 4 and it's design, causes more headaches than it ends up being worth. (like seasons and the decorations going auto on community lots etc.)

I find the only thing they did possibly do right was maybe Vampires.

Most of the time the additions become a major annoyance.