I understand what you're saying (I miss Inbox, too). But end users like sameness and "it just works." Normies prefer stability over innovation when they are trying to get stuff done.
Inbox was not deterministic. It's like a social media feed for your e-mail. I'd rather have my mails left as-is, and allow me to work with them the way I want.
You don't have to be a "normie" to appreciate simple or old fashioned things. Most of the e-mails I receive is not for quick-consumption, and I prefer the standard way over Inbox's way.
Maybe it was a solution trying to find a problem, IDK. I used it for 30 minutes tops.
Thing is, they quit on it too quickly; sure, a lot of people would stick with gmail, but others - and following generations - would adopt and grow up with inbox.
I think / suspect that many people develop habits of this type in their 20's and never move away from it for the next 60 years because it works. Example, people who still use vi(m) / emacs. Nothing personal, but as an example, they use it because they're used to it and have been for decades. And no editor that claims to be better will ever replace it for them.
Gmail settings still look like they were made in 2001. Any UX designer will want to pour Clorox into their eyes by just looking at it. Remarkable how Google can just totally ignore it, but then again - email is a very specific product. Once you grab your market share, we are locked in into our emails.
I think after inbox died I just gave up on it and moved to fastmail.