I probably have more than one thing that I would change so I'll answer this with a few important points.
1. Sometimes they change the game for other players in ways that kind of break it for me and I need to just ignore those changes if I can. I am happy for those other players and sometimes I like the changes but at other times, they interfere with my gameplay. For example, there were players who wanted a lot more sad and angry moods so I will see sims going into a rage or being tense for reasons that I don't want. We used to have whims but now with wants and fears, it can feel like I am being pressured to play a certain way. Make that sim play pop music or else they will be mad all day. There are a lot more fears than I want to focus on. I can just switch that feature off but I liked having suggestive whims. I end up using more mood-enhancing rewards to do what I want.
2. Also, they added more autonomous behaviors and while sometimes I appreciate that, it is annoying if I know what I want to do. For example, there is more autonomous flirting by sims which I end up needing to just ignore. I also had a non-playable sim dump a character I was playing. I understand that some players like that and I did end up rolling with it but it was annoying because I wanted to send that story in a different direction than it ended up going in because of the autonomous action. I don't think they should get rid of that feature altogether but I would like to be able to indicate whether I want random new excitement to happen or not. If not, it's because I already know what I want to do with that household. As it was, I let the sim be dumped and there is some social tension in the game but it changed the nature of the character that I was playing because I wanted her to be a dreamy romantic with a very sweet boyfriend. Now, he has dated two of her good friends. It isn't the same story.
3. Autonomous flirting by sims not led by me at weddings. That one is getting annoying. I have had 3 out of 4 recent weddings where weird random autonomous flirting with the bride or groom happened. In the most recent case, the groom needed to go to the toilet after the ceremony so I let the bride and groom chat with the guests while I looked for the toilet at the venue to send the groom to. When I panned back over, I saw that he had fallen completely out of love with his new bride because she had flirted with his sister in front of him. His sister was also newly married and now I will have to deal with that when I play her household. The whole thing made no sense. I have a policy that if it wasn't my action and I didn't want it to happen then an action doesn't have to count and I can ignore it or undo it. So, I just had the bride and groom make up and I will have the sister make up with her new spouse. I guess I can stick to more elopements without guests or I can pause all action whenever I am not specifically controlling the bride and groom. Other than that, I like the weddings in the game but I have found that frustrating because it ruins the mood of the wedding. I am not sending couples to a wedding to fly into a fury and hate each other unless I specifically want that plot.
Generally I like the game. I like to roll with some changes and I have a lot of fun with the characters that I have developed. I can also usually ignore what I don't want. I think that being able to manage moods and suggestions for gameplay how I want is important. As for autonomous actions, they are usually fine with me. Guests at weddings kind of need an overhaul. Maybe we should be able to choose if a wedding is happy or on the rocks when we set up the event.