So you can't link me where Blizzard states how Classic is "supposed to be played". I didn't expect any different.
Requirements does not equal "right to be invited". Only entitled people would demand and feel entitled to be invited to other people's groups and/or try to control how other people play together.
Let me link you the only place where Blizzard mentions player created groups:
" Voted out of group before I could finish quest
Removed to make space for guild member
Kicked from a Mythic+ group before receiving loot
Note: Groups formed outside of the queue system (Guild Runs, Mythic +, etc.) will not utilize the vote-kick system. Instead those groups will have one party leader that controls who gets invited or removed."
https://eu.battle.net/support/en/article/52363
You can't find anywhere where Blizzard states anything whatsoever about that you have a right to be invited to other people's groups.
You can't find anywhere where Blizzard states anything whatsoever about how you should make groups and how you shouldn't make groups.
Blizzard has since day 1 given 100% free reins to the players on how they make their own groups.
But since day 1 entitled and toxic players have tried to guilt-shame other players to invite them to their groups.