Are expansions getting worse with each Sims game?

I'm so confused as to why we are getting the same expansion packs as were released in previous sims games, yet we are missing things from them. Such as our pets expansion was only cats and dogs, and is missing horses from sims 3. In the other pets expansions there was a pet store, and I completely understand why they would get rid of it but it would be nice to even just have an animal shelter that could perhaps be run and owned by your sims. If you decided you wanted to adopt an animal you could go see all of the ones available rather than looking at the picture of their face on the computer screen. Also you would be able to bring the stray animals to the shelter rather than adopt them into your own home or just leave them all smelly and hungry on the streets.
Another example of us missing items from expansion packs would be in Island Living. I personally didn't play sims 3, but Island Living to me is the exact same as Island Paradise but without the fun gameplay of getting to run your own resort.
I'm honestly just not understanding why as the years progress they continue making new sims games when they could just make one Sims (rather than having sims 1, 2, 3, and 4) and make it absolutely perfect and including all of the great gameplay we got in previous games.
Its sad getting expansions we are so excited about and seeing that they aren't even as good as the ones from previous years. :(
Do you have any other examples of things we are missing from Sims 4 but had in previous games?