They did greatly improve the visuals of character creation, it was hard to make a descent looking sim in sims 3. How clothes work has been improved too, not sure about the needless addition of party outfits however.
But it's the personality part that took a dive. Sims are too similar. Aspirations can be changed on the fly and have little meaning.
There's no preferences, no favorite meal, no favorite color. No general lifestyle. Just something they can quickly change up.
Only three traits which is not enough, and most do very little.
I do think that sims need to be given a general goal in life again, a main aspiration that affects their general outlook on life. Like in sims 2, and a long term goal chosen after that seperately, what goals are available would be determined by their life aspiration. Would be some overlap but each should have unique goals exclusive to that aspiration.
And they should add more of that.
Family, romance, popularity, pleasure seeker and knowledge could return as they where pretty much.
Fortune could return focusing just on getting rich, being very materialistic but the business part of it could be seperated into a new ambitious aspiration for workaholic sims focused on reaching the top of a career.
Inner peace could be a new aspiration, these sims want to be healthy of body and mind.
Power could also be a new one, which can take many forms. They'd favor careers where they get to be in charge, enjoy telling other sims what to do, and might want to learn magic. They'd want power at all cost so might struggle with moral dillema's.
Some traits could be unavailable to specific aspirations, but only where it makes complete sense. A hothead could want inner peace, they'd just get extra upset when angry and want help for it.
But a sim with the family aspiration can't hate children for example.