Coming from somewhere else, US textbooks feel super watery - low signal to noise ratio, too much hand holding.

I would tend to agree with this. A combination between low-info fluff and childish presentation. It feels like being bombarded with a technicolor fireworks display of obfuscation and mystification. Maybe it's the gimmick of "edutainment" and the goofy idea that you need to inject fanfare and folderol into education to appeal to students that created this mess.

If you look at older textbooks, before education publishing became the extortionist big business it is today (like, say, Pauling's book on general chemistry[0] - which you can still get from Dover - to name one), you will find many that are lucid and intellectually satisfying. Heck, look at scholastic pedagogic texts (like the Summa[1]) and you can follow exactly what's being said. Even if you don't grasp something, or grasp it correctly, it isn't because the writing or presentation are shit. It's because you need to keep going, but you know how to keep going. You have handles on the content and not just some huge, impenetrable, and slippery orb looming over you.

It's eye-opening, because our entire media regime, and the sensibilities it entrenches, seems to suggest that education used to be dull, mindless, and joyless before the great "progressive" innovators blessed us with their wisdom, forgetting the origins of the artes liberales and some of the 19th and 20th century turns[2] that did actually debase education into something vulgar by comparison, something convenient for industry and the state.

[0] https://archive.org/details/generalchemistry00paulrich

[1] https://aquinas.cc/la/en/~ST.I.Q1

[2] I am not claiming everything was perfect centuries ago, or that there were no good pedagogical developments since then.