Better mechanics:

Changes made to vanilla minecraft:
Reworked all undead mobs they now can:

call for reinforcement if hit summoning 2 others of their kind

infect the player and make them weak.

target and kill passive mobs like pigs

added a new corruption block that spreads from nether protals upon use, corruption block can:
spread to stone, grass, sand, red sand, gravel.
infect passive mobs like pigs, villagers, skeletons and turns them into their hostile variants: pig to pigman
slow down & weaken players who are on it for an extended period of time.

reworked crafting, progression
to gather wood the player must first make a chisel by gathering fiber by breaking grass blocks or dirt, bark by stripping a log (attempting to break it), loose stone by either stone or gravel
and then make a stone axe in their crafting grid, get or make string gather even more loose stone and bark and finally make a chisel and be able to mine stripped wood for a single plank. crafting a single ingot for ores now requires the player after smelting the raw ore make a piece and then with the piece craft an ingot

reworked enchanting
you no longer need book blocks for enchanting its all random now.
enchanting requires a scripture which you can acquire by trading with villagers however if you didn't get the type you wanted you can trasnform it into another type via your crafting grid just put any scripture in with a stone tool next to it
or copper armor.

misc changes:
spiders now have a chance to spawn webs upon damaging an entity.
mobs have a higher chance to get armor upon spawning
the dragon can summon shulker boxes upon being damaged
the player now gets hungry much faster than before.
after the player gets killed by a zombie
a zombie will be summoned on top of the players corpse.

future updates:
anvil rework,
brewing rework,

better mechanics