If you could change anything about Terraria, what would it be?

[Marrow]

I'd make the tiers a bit more grounded and less easy to like... skip over.

Ore armors are a ing joke, they're so goddamn expensive. Just run on over to the corruption with some bombs you found while mining for 15 minutes, break an orb, save a bomb for the demolitionist and get him to move it, and then buy some dynamite to destroy the meteor that falls. Then boom, ya got armor and tools that are good enough to defeat the WOF.

I agree with you. To make a playthrough more balanced you basically have to restrict and make rules for yourself- which is kind of annoying. Plus even if you do use Ore armor, by the time you have a full set of something like iron, you've probably already collected enough gold to make yourself a full set.

 

[Unftf]

and remove the Old One's Army.

Why?
I like it in some way. But most dropped items you don't need anymore if you are able to get them. But what I would like to change is that you get points like in moon events. Besides that it should be the same spawn order each time like in any other TD. So if you do the same, you will get the same points in each run. At Moon events your score is very luck-based. If you do the same setup multiple times the variation of your score is very high.

Besides that there could be some variation as a post-Moon-Lord Event (without any new item). So you overpowered Moon-Lord drops have some usage. There you need to defeat each boss and each enemy in as short time as possible. With points again. And the same spawn order at each run. Item drop rates reduced.

and 2.) There should be some blocks for NPC Flats, which don't block the user in vertical movement, e.g. something like bubble blocks. But currently you can't use them for a valid NPC house.

 

[Tarluk]

I would change the way Corruption/Crimson spread into the jungle.

Instead of turning Mud into Dirt and then Jungle Grass into Corrupt/Crimson Grass, the Corruption/Crimson would turn Jungle Grass into Corrupt Jungle Grass or Crimson Jungle Grass.

The same mobs that spawn in the world evils would spawn in the Corrupt/Crimson Jungle, albeit with a few Jungle mobs resprited to look like Corruption or Crimson mobs. Maybe there could be a Corrupt Plantera that's harder than normal Plantera (the difficulty being in-between Normal and Expert mode Plantera)

 

[Madgems]

that evil choices would actually have an impact on your npc's or boss selection
(for example if you spread corruption the dryad would dislike you or even try to fight you)
(or if you do "evil" desicions you would fight "good guy" bosses or invasions)

 

[Shrek On My Deck]

I would want to add a bunch of new bosses, items, events, and biomes. I think that would make the game a lot better without having to download mods
bosses:
Brimtwins: fought at night after ML is defeated
crystostorm: fought in hallow
ice phoenix: fought in the ice biome
sun lord: moon lord's counterpart
galaxitail: a dragon fought in space
demon lord: fought in underworld post ML

Biomes:
mountains: high, rocky, rough terrain with chasms leading into large caverns
deeplands: under the mountains: large cavernous biomes
crystal caves: located in the underground hallow, massive crystals!
ancient forest: tall trees, lots of shadows, dinosaurs
dwarf cities: randomly spawn underground

events:
soul hunt: at night: lots of reapers come out
harvest festival: thanksgiving, unique items are sold
armageddon: any time, the world is falling apart!
cosmic starfall: comets rain down

If you have any more suggestions, please let me know!