The best software around is Emacs. Does that count as "opinionated" in your view?

In some ways it is—Emacs does a lot of things its own way, completely unbothered by mainstream conventions—but, at the same time, it's also totally malleable in the sense of this article. What makes Emacs great is a consistent and coherent conceptual foundation coupled with remarkably flexible code, letting you adjust Emacs to your needs rather than adjusting your needs to Emacs.

Or maybe the best software around is situated software. Software that's built by and for a specific set of people in a specific social context. Situated software is qualitatively different from product software, and it works so well because, again, it gives its users real agency and control. Instead of trying to create software that knows better than its users, we can create software that supports its users in whatever ways works for me. The result is still opinionated, but it's opinionated in a categorically different way from what you're describing.

So perhaps the best mainstream software is Excel.

And, while I don't think they're there now, it seems like LLMs are likely to be the foundation for the next Excel.

You can either go with simple primitives and a way to combine them (emacs, excel, unix) or simple program that just works (notepad, sumatra,…). Anything else is going to be restrictive in one way or another.

As a vim user I agree with all this. Same is true about why I am terminally terminal. I'm able to adapt the tools to me so that I may get the most use out of them. Sane defaults are great, but there are no settings which are universal. The only solution to this is to let people adjust as needed.