And that's why the Core Four DMs need to make these things themselves (or find 3PP versions out there to use) if they really want them that badly or think it's a better way to play the game.Just using the core four in the PHB doesn't work, though. The other classes have to become part of them in some fashion. For example:
Fighter, add subclasses for Barbarian, Monk, and Ranger
Cleric, add subclasses for Druid, Paladin, Warlock
Rogue, add subclasses for Bard, Monk, and Ranger
Wizard, add subclasses for Artificer, Bard and Sorcerer
Some classes, depending on concept/role, such as spell-less Ranger vs magic Ranger vs. whatever Ranger might fall under one of the four core classes or another.
I know we've had homebrews that made Barbarian a figther subclass, Warlocks a cleric subclass, and Sorcerers a wizard subclass.
So, in short you can't just "remove the other 8 PHB classes" and still have all the concepts you'd have with the other four alone. Those other concepts/ roles need to be incorporated into the four to make it work.
But do any of them do that? Doesn't seem like it. No one seems to ever bother to make the base game into the game they want it to be. Which means one of two things-- either their desire for only using Core Four + subclasses isn't as important to them as they keep clamoring around here that it is... or they know as well as the rest of us do that no one actually thinks Core Four + subclasses is a better version of the game.
If (general) you needs Wizards of the Coast to produce the idiosyncratic version of the D&D game that you want to play in order to get players to play it... that's a pretty good indication that your idiosyncratic version of D&D probably isn't actually that good.