Seems like we have like 800 natural and artificial gums, flours, emulsifiers, etc, some of which are even occasionally considered health food ingredients, and most almost all of which seems healthier than sugar, why not use those for the baking texture if you're going to use the fake sugar for sweetness?

I suspect you slightly under-appreciate how ubiquitous sugars are in nature. Glucose and its close relatives are everywhere in plants. Cellulose, the main building material of plants, is polymerized glucose. A ton of various substances of plant origin are all pre-built to interact with sugars, and may have trouble interacting nicely with severely different kinds of molecules.

With relation to baking and frying, https://en.wikipedia.org/wiki/Maillard_reaction works with sugars, and likely can't work adequately with something materially different.

Does Maillard actually do anything aside from the crust? Why couldn't we just put a tiny but of real sugar in the top few mm, by spraying sugar water or just sprinkling on wet batter or dough?

Seems like there are commercial sugar free stuff with an ok texture, but then again maybe I just haven't noticed because the taste of most artificial sweeteners is so bad that it masks it, and I only try them if I accidentally buy something with it...

Because those don't give you the same outcome as sugar baked goods.

I urge you to try and bake with any any of those 800 and get a baked good that has a texture like a sugar based good (and doesn't totally crumble apart)