I found the blog post a bit annoying because it was clearly trying to win internet points rather than actually solve a problem. What you wrote above would have resolved the issue in a couple of minutes, faster than moving over to another email provider. I found all the Gemini integration into consumer products super annoying as well and disabled/unpinned all of it months ago the day I noticed it and thought "wth is this annoying thing". Now, if/when Google removes the option to disable, this blog post would be much more impactful IMO.
The author did say he tried some settings but not everything was available to disable. I dove deeper into it here [0]. You can disable Gemini AI and others and there is also a "nuclear option" where you disable all smart features.
Yes, I disabled all smart features. I'm surprised anyone here (or the type who bothers customizing their inbox layout) finds the Primary/Social/Promotions split useful. The original blog post mentioned "automatic thread categorization", which I thought just meant grouping emails in a conversation together (which doesn't really require any "smart" logic).