This isn't going to be how everyone feels - but some of us are feeling a real pain over this situation. I'm just asking people to consider that when they write about the situation.
I started with OD&D even before that, in 1977. Admittedly, not as hard core as it became in the summer of 1980.
But I left 1st ed in 1984 for Rolemaster. I skipped 2nd ed in its entirety. Came back with 3.0 in 2000 - jumped to PF1 in 2009, to PF2 when that came out, and just to 5e last March.
It's ALL D&D. The people who make it are incestuously employed across these companies. Monte Cook was with ICE for several years in the 90s writing Rolemaster Companions - before he moved on to TSR and later WotC - and wrote 3.0.
The 3.x I fell in love with had nothing to do with those hardcover books -- it was
Dungeon Magazine under Paizo that gained my deep attachment. And at the time? Erik Mona and James Jacobs spoke for the D&D brand in the magazines.
Pathfinder was always D&D. PF1 was just 3.5 in an altered and improved form. The people who made it - and who wrote those Adv Paths were the same people who had written
Red Hand of Doom and
Age of Worms.
Am I attached to a trademark? No. No I'm not. And I suggest to you that if you are, that's a problem you need to get by. I would never suggest you shouldn't be attached the rules, the style of play, the subject matter of the game, or the creative talent who did all of these things. You can and you should be attached to those things.
But let's get real here: most of those people cycle through company to company : from Wotc to Paizo and back to WotC -- and maybe back to Paizo or Kobold Press or wherever -- the people who are making D&D and near clones of it are the same.
At its core? It's a small hobby.