IIRC This was suggested before and was also discussed before in non-suggestion posts
These are optional, so you're not forced to beat them. The loot you get from them are still pretty useful if you do need them, like the Kaleidoscope and whatnot.
Kaleidoscope is one of the very few because stardust fragments doesn't let you craft a whip(well, until 1.4.5), you don't need Tsunami because you can get Phantasm easier to obtain and better, You don't need Razorblade Typhoon it's easier to get Nebula Blaze, Don't need Xenopopper or Chaingun because of Vortex Beater and so on
Pillar weapons are easier to obtain because cultist is too easy and unlike bosses pillars doesn't reset your progress when you die
After all every single pre-HM boss is optional. You can get dynamite or Demon Scythe + Jungle armor and kill Wall of Flesh as your first boss. Nobody makes you fight ither ones.
Post-Golem you just kill Skeletron for 5 seconds, spawn Cultist and then Lunar event.
It's not this simple for any class other than mage, mage can get top tier pre-hardmode armor and best weapons at the start.
Dynamite is considered a cheese, Jungle armor and Demon Scythe isn't enough. Unless you're really good at the game or playing in a difficulty that's too easy for you, you'd also needs accessories.
I wouldn't step on jungle before exploring usual underground/sky islands for some loot, I'd at least get a hook and a decent weapon, because hornets are too tedious to deal with wood tier loot. When you do some underground exploration and get some loot, you might aswell fight EoC(and maybe slime king) before jungle armor because it's not that difficult with your current loot plus some evil ore, dryad and Shield of Cthulhu would be nice to have, same goes for Eater/Brain they unlock hellstone related upgrades so why not, then skeletron gives access to dungeon and shadow cheats, so many useful loot against WoF gives best weapons against wall for non-mage classes + cobalt shield.
In pre-hardmode it makes sense to beat easier bosses before WoF because their upgrades are valuable against WoF, sometimes they are useful even in early hardmode (like cobalt shield, pheonix blaster) but when it comes to cultist bosses/challenges before him are more difficult than him but upgrades are weaker than what you get from cultist and pillars.
So they aren't worth doing in most cases unless you force yourself to do them and pretend like they matter so pre-cultist content aren't wasted.
EDIT: Also OP's suggestion will make all Terraria speedrun records irrelevant. Speedrunners won't like more mandatory steps to Moon Lord.
Devs don't have to care that much about speedrunning, plus I don't think they'd hate it unless they hate playing the game because that slows down everyone's speedruns not just theirs
This is not that bad. I think Moons, Duke and Empress should remain optional.
Yeah they should remain optional, I think buffing cultist is the easiest solution, a major buff. I'm thinking a damage increase and make it almost impossible to spot & attack the right clone before summoning the dragon.