All the monster i said its required for the World/Iceborn Plat but you are right, some monsters like Rage Brach, Kulve, Rajang arent needed for the plat and yes you have some fixed events with guarantee crowns, but the easy part ends there.
Also im talking here from the average player ( me ) POV, the problem with World its that endgame monsters ll need some anti builds and there is no 100% guarantee rarest itens from investigation like Wilds and monsters drops way less resources. Lets say that a player want to make an end game stick HBG build to deal with Kushala, he ll look at the internet for builds and aside from Fatalis and Safi weapons lets see what do we have:
Demonlord Beastbuster: Furious Rajang
Magda Gemitus Vulcan: Zorah
These two grinds alone ll make a lot of ppl give up on a stick build, for Demonlord you ll need a Rajang Heart to make the weapon and while the drop rate of the heart is high ( 9% ) the average player ll probably die a lot in this fight since it a Furious Rajang Drop, Magda is easier since the Large Elder Dragon Gem have a 16% drop rate from elder dragons on gold investigation, the problem its that you ll have to open guiding lands to get all the material needed for the weapon. There is no such specific weapons needed to cheese Wilds Monsters. And i ll not even talk about deco farm in world vs wilds, you see, World another beast to be conquered, it ll take more time since it ll require more grind from the player, fights are way harder, Kushala and Kirin ll frustrate players if they are not prep, in comparation Wilds grind almost doesnt exist, fights are easier and fast, almost everyone has endgame gears and weapon, there is no such thing as deco farming in Wilds, they give you decorations in droves.
Also there is other trophies that ll 100% burn you out.
Wilds is a way more forgiven game and way less grinder and thats why imo we have more plat % on it.