I don't understand why you need to start again. If you wan to play a new sim, just add him/her to a new lot in the same save. This way you have sims that you can choose from for friendships and marriages and they come with some skills and interests and a backstory. And you can always return to them if you get new ides for them.
I have never had updates break the game to the point that it becomes completely unplayable, but I play vanilla. Sure, there are bugs, but when I want to play, I try to play around them if possible. Sometimes I just build interesting community lots for my sims. They are more fun and more elaborate and diverse than tying to fit all skill and fun objects onto the home lot.
For poor sims who become rich and are no longer interesting, maybe you could try change your game style and aim for different achievements than just financial. Give them a job, hobby, or aspiration that maybe you have never tried playing before. When new ideas arise, see if you can apply them to your current household and incorporate them into the gameplay. Sometimes even small things like adding a lot challenge to the lot can change the gameplay enough to make it interesting. When you get bored with your current family and run out of ideas for them you can switch to another family in the same save, it could be a new one, or one you have played before and for which you have some fresh ideas.
