I also tend to focus on particular Sims and never let them die haha I like to play families through generations, but my founders outlives them all. I just don't have the same amount of involvement when playing Sims born in game. You need to set all those outfits and they never look quite as good, then they die really fast, I'm too lazy for that.
Have you tried going after the collections? It's 1000x harder than just maxing the skills or related aspirations. I'm trying to complete all of them with my supersims alien family, they really take it seriously the mission of exploring our planet :p it's a mindless grind, but I find it relaxing and for sure will keep your sim occupied while the rest of the family goes their own way.