Cause HOMM3 is heads and heels better than all that came after it. You have some that need UPlay to be connected at all times. Fine, whatever. But then they have a cash shop in others for stuff that should be basic ass rewards. Ok, rustled, but fine.. again. But then the time it takes for the AI to complete its turn takes fucking forever.. not because your PC is slow, but because they changed something between 3 and the later editions. Then you have the maps which have progressively gotten more cluttered with graphics that actually make it harder to see important shit on the map. Then the ability for Heroes to depart from your armies, which is fine in games like TW Warhammer, but not in a game where you need to be exploring and collecting shit on the map. (You have to do this on harder difficulties cause the AI is forever trying to play fucking cat and mouse with you. You cant collect or claim resources without a Hero. But yet a single hero can run around the map doing shit, which makes cat and mouse tactics powerful af.) Never mind that the talent system has gotten progressively worse since HMM3. Then, the factions themselves have gave way to homogenous attributes. Instead of the Rock / Paper / Scissors type of play style that three offers, in later editions - you just have straight up "400 units of a tier 4 unit VS 401 units of a tier 4 units = 401 wins" (without hero in foreign land).
Hell, I havent played the most recent version since 2017? 2018? Yet I can still rant off a county mile of bull shit that has ruined the HOMM franchise. Should have realized how bad corporate was fucking with it when they changed the name to MM:Heroes in order to get some eyes from the regular Might and Magic franchise or vice versa. Never mind that they've went full blown Mobile game and Might and Magic: Era of Chaos is raking in the fucking bucks.
