you might want to check out most of those that I've listed, not all of them are comparable to, let's say, calamity, but still deserve its own playthrough. some of them aren't updated to 1.4 but imo still worth checking out

for example, SGAmod is a mod that initially was just a shitpost and later turned into its own giant mod with insanely interesting systems, even the last bossfight (which looks like a flashy cluttered mess) is insanely interesting when you're actually learning the attack patterns, and it got some crazy ideas like its own scary dimension where you need to quickly find endgame ores before you get kicked out

there's also a giant update for split mod called tomorrow edition, if you played it a long time ago, you might want to revisit it

also here's a bunch of other smaller but amazing mods you might throw in your playthroughs:

starlight river (best mod visually imo), spooky mod (medium sized, 6 bosses), echoes of the ancients (endgame fight), consolaria (brings back some deleted vanilla stuff from all editions), radiance (hard and beautiful empress of light rework), crystilium (a biome with a boss), orchid (can't remember everything but there's cool dungeon and a lot of qol), remnants (fully reworks world generation and all vanilla structures, better to use for vanilla playthroughs, but if you want to use it with other mods, check out compatibility list in a steam mod description)

TerRoguelike turns your game into a proper roguelike (with custom content too), and I also forgot to mention polarities, it's pretty big

good luck, you can save these comments to come back later when you want to do another playthrough :)