I'm not entirely clear on the conclusion you're drawing here and I don't want to misunderstand- it seems like you're saying that any game inspired by D&D is D&D, even if it's made by other people. Does genre or ruleset make something different enough that it isn't D&D?Shhh... don't tell anyone, but any game made with D&D rules is pretty much a D&D variant/clone, and all D&D is D&D, even if a 3rd party wrote it or if a particular individual isn't fond of its presentation.
Knave! and Into the Odd could trace their lineage back to D&D and share the fantasy genre- are they both D&D?
Star Wars Saga Edition was made with d20 rules which were originally D&D rules, so when you're playing Star Wars you're actually playing D&D?
d20 Modern- that was made with D&D rules, even closer than SW:SE. You're playing D&D, not d20 Modern?
The last two examples are very close in system, but pretty different in genre- I'm curious how far of a connection you'd make between any other TTRPG and D&D, considering that D&D was a foundational ruleset for TTRPGs which many other games have since sprung off of, or been inspired by, even if they lack genre or rules in common.
I guess the question is where do you draw the line, since you say that any game made with D&D rules = D&D variant = D&D?