I definitely do not agree with that assessment. Outside of the challenge areas pretty much every single puzzle exists to teach you something about the mechanics, or the conceptual space of the puzzles, even if what it teaches you is not necessarily helpful to completing the game[0]. The challenge sections of course are meant to test your understanding.

> It didn't help my opinion that it goes for the modern writing story writing trope of "say a bunch of interesting things but use player agency as an excuse to not actually tie them together into a coherent narrative with events and consequences".

I can see how you get that feeling, and truth be told so did I early on in my playthrough, but I really don't think that's the case here at all. It's more like, the things that Jon is trying to communicate in The Witness simply do not lend themselves to easy explanation and are, in fact, kind of difficult to fit into a mental framework that demands concreteness in the first place.

As far as tediousness, I think the key there is that it is probably not a good idea to try and play in long sessions. Certainly the longer I would play the more I just kinda wanted the game to be over, at least until I quit and came back to it. The Fool and His Money[1] often makes me feel like that after a single puzzle, so I don't think The Witness is that bad in this regard.

[0] Some of the puzzles are jokes, or even a commentary, told in the language of the puzzle.

[1] I think I've been playing it for 2 years now, and I'm still not even half way through.

I don’t really enjoy solving the puzzle simply for the sake of the puzzle.