Sparse compared to what?
Wotlk:
-New class
-New profession
-Achievements
-2 new BGs
-Barber shop?
-Vehicle system, I guess if you want to count it as a 'feature'
MoP:
-New Class
-New Race
-Talent revamp
-Scenarios
-Pet Battles
-Challenge mode dungeons
Legion:
-New Class
-Artifact weapons and their progression system
-Mythic+
-World quests
-Class Hall campaigns
-New honor system
-Transmog update
Dragonflight:
-New Class
-New Race
-Talent revamp
-Dragonriding and its progression system
-Profession update and new gearing/progression system
-Reputation-Faction campaigns