This is a slam dunk, and a great reminder of what Spelljammer has always been about.
I wonder if some of the people turned off by that unabashed silliness are just overly caught up in mapping their RPG identity and interests to a single publisher? There's more to fantasy RPGs than just D&D. Hell, there's more to D&D than just WotC. And cherrypicking one's memory of past D&D stuff that aligns with your tastes is kind of a problem. Hindsight isn't actually 20/20, and neither is nostalgia.
I also wonder if part of the issue is the way products are announced and discussed now, compared to whatever era someone might remember as their golden/formative age of D&D. When Spelljammer was first released there were no forums for breathless anticipation and guesswork about every single upcoming D&D product. And when something did come out, it was easy enough to look at the cover and say, Huh, guess that's not for me, and move on. There was less hype, in part because there were fewer ways to broadcast and consume hype. For example, I never saw Spelljammer space hamster art back in the day, because I noped past Spelljammer without even cracking it open. But I also wasn't feasting on hype and speculation--not because I had better things to do, mind you. That just wasn't an option.
To me, being disappointed that WotC isn't living up to your specific expectations, but continuing to closely follow their every release, hoping things will turn around...that seems like a self-inflicted wound.