Thank you to Bflury on TS3 Forums for organizing this list! I fixed a lot of spelling/grammar/writing issues for you guys…enjoy!
Everything below has been 100% confirmed, excluding the final category.
This is a list of features that were COMPLETELY CUT or REDUCED from previous iterations of The Sims. It DOES NOT include missing expansion pack content that should be base by now (i.e. Weather) or new features promised for Sims 4 that were later cut (i.e. Woohoo Skill).
Lastly, it is important to understand that much of this content will NEVER be in The Sims 4. Things like Create a Style are not compatible with the game engine, and thus cannot be added in future updates or expansions.