As far as other excuses such as saying older meshes were easier and or building the game (for whatever they needed to do) is harder this time. EA also didn't pick the engine, nor the software tools such as Python, nor did EA pick to let go of any engineers that's all on Maxis.
Not excuses or blaming EA, that's just the reality of a more up to date game. Making smoother animations and creations takes more time than making clunky lower res ones which means they can create less in the same timeframe.
I see this here all the time (bolded). How do any of us know this? Way too many restrictions? Who says? They are pushed to make so many different packs every year and EA doesn't give them time? Who says? Are they pumping out more than TS3 teams? Or as fast?
They don't get enough resources, again who says? Only thing I ever heard from an ex developer for TS4 was that Maxis (not EA) had hired too many producers and not enough developers.
Why would any games developer cut back and put half baked content out by choice? They want the game to be the best it can be like players do because the game is their creation. It's the company and higher ups that pay their wages, the developers don't make less if they put out less packs it's the company that makes less.
Last year there was $130 worth of packs released, 2018 $120, 2017 $110. There's a clear theme of how much value they have to put out every year. Guessing they have to meet this value of packs per year which would be set by a higher power than the devs. Obviously this means having to meet deadlines. If they had a larger team and more resources they could achieve more in the given time.
Their ambitions being cut short is most clear from Island Living, it's clear they had a lot of things planned and ideas that they wanted to put in but didn't have the time to execute it properly. For example with this pack it had to be ready by summer, which is probably why they didn't have enough time to fully bring everything to life.
Just look at the bugs team if you want an obvious example of not enough staff and resources, they're always working on stuff and issueing patches once or twice a month and there's still bugs. If they had a larger team more bugs would get fixed.