Negatives:
Memories gone - replaced by taking a picture to inflict biopolar story telling
Moods gone - Replaced by the bipolar disorder system seen in TS4, your sim no longer has any form of gradual or overall mood
Wants gone - Nothing your sim wants to accomplish that has impact on their life or makes them happier, they just want to hear the radio so you can buy them an empty perk later
Fears gone - tragedies and fears no longer exist, your sim will be sad for 2-3 predetermined days and forget about it forever thanks to lack of memories
Open world gone - Originating from TS3 you are now confined like good old times
Meaningful aspirations gone - Replaced by a system that should arguably be better but the easy difficulty makes it too non disruptive and its not rewarding enough with no impact on Sim life or mood
Create a style gone - originated in TS3, great feature. Can live without it but helped flesh every sim in style more to be unique.
Intricate relationships from TS2 gone - Your relationship is now two bars, "friends" and "romantic". You no longer have meaningful relationship states that effect how relationships progress or decay or unique interactions. If you become GF/BF etc it just a tag to say "don't cheat on me", if you marry it just means the same thing but now you can divorce too.
Large expansions - content heavy expansions gone replaced by gimped versions of each theme from the past. We got "Get Together" which is basically a gimped zoomer edition of Nightlife. Only expansion that has some arguably impressive feat is Pets.
Personality Points+Zodiac - TS2 era feature that gave your sims some personalized animations as well as behaviour patterns and affected their compatibility with others. Extended to their wants/fears and dictated what would upset their mood too.
Positives:
Nice build mode - Best in the series
Nice Create a sim - Best in the series (looks only and function only, best with CC to make the game not ugly TS4 style)