For me, it isn't about the imprimatur of the WotC trademark.
It's about the fact that what WotC releases has greater reach than an identical product released by a smaller company. It will shift conversations and discussion far more than a release by a 3pp.
I'm on record as saying there is a ton of 3pp material that I think is straight up better than what WotC releases. But I'm not going to pretend that a release like a Tasha's or a Xanathar's hasn't had a much greater impact on the D&D community than any 3pp product, no matter how much better design I feel the 3pp has had.
How we reach people about the hobby is a different topic than the focus we have on D&D branded versus non-D&D-branded settings as GMs. I've introduced a lot of people to D&D and RPGs too and I don't think its any harder to talk to someone about running a campaign in Midgard than it is to talk to someone about running a campaign in Ravnica. These worlds aren't ingrained in the zeitgeist like D&D is.
I also think we can work on how we bring the wide range of awesome RPG products to people who got in through D&D.
And while I'm a consumer of the product, I'm just as much, if not more, a consumer of the zeitgeist around play and the community. That's why I'm here on ENWorld, after all. A WotC release is always a central driver of those discussion currents.
Sure, it's fun to pontificate about what WOTC is going to do with D&D.
I like to think of it as its own hobby.
This ignores the ease of evangelism.
Having to consistently answer the question "Is this D&D?" when you talk to normies with "It's kinda like D&D, but not" is exhausting.
I've done it and I don't find it exhausting. I find it exhilerating to show folks how wide this hobby can be. But we're not talking to non-RPG players about RPGs. I'm talking to existing GMs and the worlds they're considering for their games.
Sometimes people like liking things and one of the things people like is D&D.
One can want official D&D settings that explore new motifs while still supporting Southlands or City of Arches.
People can all want what they want. Sure. It disappoints me when people (including myself!) want something that another publisher has done (or they haven't even considered what those publishers have at all).
Oh yeah! People should totally check out City of Arches...
I can still mix and match my 5e ecosystem game while wanting to see the ampersand on expanded Strixhaven, expanded Radiant Citadel, romantasy, urban fantasy, ecological disaster.
Arguing against people enjoying things doesn't grow variants
I think helping people realize that there are many awesome products from many awesome publishers grows the hobby. We don't have to knock WOTC to do it but many people take the idea that we should treat products equally as an attack on D&D. It's not.
Yup. I admitted as such -- along with admitting it is a little silly.
Often, our love for things we discovered in our formative years (I discovered D&D at 10 via the Red Box) is a little irrational. It is anchored by nostalgia and even a little melancholy. There IS something about that ampersand sometimes, even in full knowledge that lots of companies and people do it too and sometimes better.
I have that same draw, of course. D&D was my first real RPG back in the 80s and I had a great time. I've loved it ever since -- every edition since 2e. But I also try to ensure that whatever WOTC does or doesn't do with D&D doesn't dictate my joy of the hobby. I also don't want to hold WOTC products at some mark because of the D&D logo when I know other products should be equally treated.
I have bought, read, played, run and written for many different games, and there are many that I love dearly (as much, or even more, than D&D). But none of that changes the simple fact that what D&D is to ME, is deeply personal and nostalgic and I really, really do take great joy in loving something that comes out for D&D with D&D on the cover.
I will stop beating the dead horse now. I just wanted to reiterate it one more time.
Hasbro certainly loves that nostalgia to the brand. I suppose that's what branding is.
My desire for WotC to come out of an official setting is that Magic: The Gathering's creative team and art direction has been killing it in the last ten years and that WotC clearly has the chops and resources to do more investment and open-ended exploration in finding something new and exciting people which will entice people to come and play, rather than retreading Ravenloft, Greyhawk, Forgotten Realms, Eberron for the umpteenth time.
I think more MTG settings is a good idea for a lot of reasons. As you say, they already have the art and IP. They also have players who know those worlds but might not be playing D&D. It's a good top-of-the-funnel way to bring more people into the hobby so they can see what D&D brings, then see what other publishers can bring to the game, and then enjoy lots of RPGs.
This sort of thing is the role I like to see WOTC play -- bringing people into the hobby. Stranger Things, Heroes of the Borderlands (now coming out in five languages), the MTG settings, and so on.
WOTC can bring people into the hobby and we RPG evangelists can show them how wide that hobby can be.