I think purely stat-based armours are extremely boring and that every armour should have a set bonus that meaningfully affects gameplay or a relatively unique stat bonus you can't get easily elsewhere.
The armours from the Old One's Army, Moon Lord, Hardmode Jungle and Dungeon, and alternate ores are all great examples of what we have already - set bonuses that are noticeable and enable specific playstyles or have specific buffs that feel great to use.
But then there's... All the pre-hardmode armours excluding Shadow, Crimtane, and Meteor. All the hardmode regular ores, etc.
Honourable mentions to Angler, Mining, Snow, Gladiator, Molten, and Cactus which have some interesting bonuses.
It'd be nice if pre-hardmode class armours got a glow-up and received better bonuses, like Necro armour making mini Skeletron hands slap enemies in melee range away, or something.
Why isn’t this in game already?