I'm not trying to 'badwrongfun' anyone, I'm just stating a simple fact. The people who run D&D say that all D&D games fall under the umbrella of "the D&D multiverse" because at their core they are all D&D games. Anyone else can say otherwise. But those folks are never going to get the powers-that-be to stop saying it, no matter how much they try and deny their game of D&D is a part of that multiverse.The idea that it’s “dnd multiverse or don’t play dnd” is one of the worst takes I’ve seen on this site in a long time.
Which means the only way it is possible to have your game not get put under the "D&D multiverse" umbrella by those who claim it is, is to just not play D&D. If you don't play D&D, they won't say your game is part of the multiverse.
Either that... or just keep playing the game you always have, say that your game is a completely separate entity, and begrudgingly accept that some people are going to say your game is under the umbrella anyway whether you want them to or not.
If I had to guess, that is exactly what you and others do, because you're still playing D&D. At the end of the day, neither side has any choice in the matter-- you can't stop them from saying you are under the umbrella, and they can't stop you from saying you're not.