It's always interesting to see how players define gameplay because it varies for everyone. The Sims has always had a community of builders who hardly ever actually play the game, and for them, building is their gameplay. So getting offered new build/but styles is exciting for them.
Some people really love interactive objects and setting up rooms full of activities for their Sims, especially if they don't like to deal with loading screens or if they have a slow PC that loading takes too long and they don't like traveling to community lots. So those types of objects are gameplay for them.
Some players are stylists and spend hours and hours in CAS designing and dressing Sims (I am part of this category though not exclusively) and really enjoy getting new or unusual fashions and costumes. (I do have a few kits myself, can't remember the names but the two Asian styles kits are my faves.)
Then, of course, there are the players who want brand new things to do, new interactions, new systems, new features and mechanics. I think this is a pretty large category, (though I could be mistaken,) and tends to include many seasoned Simmers who have played other versions of the game. (I am also in this category.)
I've also seen some players who consider new animations and world environments to be gameplay, who are more engaged with the visual aspects of the game and new scenery and find that these things alone can refresh their gameplay. (I probably fall into this as well.)
When you think about it, there really are a lot of ways to enjoy a Sims game. It's no wonder the devs can't keep up, lol.