"added in the past decade" is 1.9 to now (1.8.9 released on 9/12/2015, 1.9 released on 29/2/2016).

Things "that anyone really wanted" (By which I mean the highlights of Minecraft additions):

• in 1.9.x:
  • The offhand and shields
  • Attack cooldown
  • Mending
  • Elytra (fireworks didn't work on them until 1.11.1)
  • Removed Herobrine
• in 1.11.x:
  • Shulker boxes
  • Totems of undying
  • Observers
  • Firework elytra boosting
• in 1.12.x:
  • Concrete
  • Recipe book
• in 1.13.x:
  • Swimming
  • Bubble columns
  • Phantoms
• in 1.14.x:
  • Rerolling villager trades
  • Other villager improvements
  • Raid farming for renewable totems and easy emeralds
• in 1.16.x:
  • Netherite
  • Piglin bartering
  • Fast automatic food farm (Hoglins)
• in 1.17.x:
  • Moss
  • Copper
  • Waxed Lightly Weathered Cut Copper Stairs
• in 1.19.x:
  • Sculk sensors
  • Allays (Non-stackable item sorting)
• in 1.20.x:
  • Calibrated sculk sensor
  • Amethyst sculk resonance
  • Bamboo wood
  • Armour trims
• in 1.21.x:
  • Crafter
  • Bundle
  • Happy ghast
  • Shelf
  • Copper golem

ㅤ

Mods? The features I think mods probably would not have done equally or better, or would not have come up with something as unique, are:

• Offhand
• Removing Herobrine
• Raid farms
• Piglins
• Sculk sensors

ㅤ

Others that idk whether qualify for the list:

• Mending
• Recipe book
• Villager overhaul
• Moss

ㅤ

(I'm talking hypothetically about mods here because I have not played old modded (or old versions at all, the first Minecraft version I played was 1.13))

(This is just my opinion combined with comunity reception of things, I'm not trying to argue)