Prehardmode I disagree with but yeah, I feel like the Pirates should be something that only happens after you beat a single Mech boss. As being underpowered and fighting them is just an unpleasant experience.My favorite part of the game has to be whole pre-hardmode. Starting pretty weak and upgrading your character feels very satisfying, specially when u get better accesories to improve your movement. I also enjoy how important exploration is, and basically looting everything on sight to get stronger. Making houses and setting up a pylon network is also nice if you get more creative than just making a bunch of shoe boxes and NPCs. You can be pretty relaxed and take your time.
In contrast, early hardmode (pre mechs) is kinda boring for me, it's just ''rush to the crimson to break altars while dying a couple of times in the process, get just the right amount of stuff to skip Cobalt and Mythril entirely, die several times again, rush back to the crimson to break more altars because Adamantite gear is too expensive, die a bunch, and repeat until you get Adamantite stuff.'' And then you have to farm a bunch of souls to make the boss summons. And the pirates can invade you anytime while you are doing this. And the Corruption spreads pretty fast, too.
For me at least, it's a pretty monotonous stage of the game, though getting wings is pretty amazing.
Playing Terraria for the first time has a certain unbeatable and unmatched charm to it. And the mask of Pre-Hardmode exemplifies that. Pre-Hardmode has such a charm to it's simplicity and wonder, I've probably spent hours in it or reflecting on my first experience with the game way back then... Nostolgia aside it's finnominal.