And yeah, this is just my personal view. I didn't say it is what it should be or how it actually is. Nothing sweeping about it. Simply how I feel based on my experience.
Spiders aren't insects, as I would have noted earlier had I been closer to awake when I posted my prior comment. They're arachnids. Arachnids and insects are both arthropods, but are no more closely related than that. It's not a rare confusion among laypeople, but it is also among the first things anyone learns in the study of either class. That you do not know it bodes ill for all that follows.
You mention spiderwebs, which is especially remarkable because they are certainly among the best studied examples of unhuman engineering. Relevant research isn't hard to find, and you will if you feel like it; rather than dig up the same links you can, I'll tell an anecdote that bears them out.
A couple of years back, an orb weaver began building her web on my porch every night, for the moths and flies drawn by the light from the front room. Because she opted to build right across the steps down from the porch, one night I faceplanted the web and broke a few strands extricating myself from it.
The next night and every night after, she built in the same place, but not in the same way; instead of the classic round orb-web shape, she built wide and squat across the top of the space, retaining about the same prey-capture area and staying within the volume that was busy with potential prey, but with the lower edge of the web now about six feet above the porch floor.
That's an interesting figure, because it exceeds by a couple of inches both my height and that of my partner at the time. The spider had no opportunity to size her design to us by eye, as neither he nor I was on the porch while she built this way the first night, and orb weavers' eyesight is far too poor for such a task in any case; by the time we came along to sit on the porch that evening, she had already finished her work.
To build as she did, then, she would of necessity have had to understand and remember the spatial relationships involved in my face getting stuck to her web, and then on the next night implement a novel modification to her design such that we could and did pass beneath without conflict - not just with the web itself, but also with its guy lines, none of which crossed the space below the web despite the newel post finials offering a very obvious and easy pair of anchors. And all this while working with useful visual acuity in the span of perhaps one or two centimeters - to a scale which, in our terms, would be that of about a ten-story building.
This is not the behavior of a creature operating solely on unconsidered instinct. I can't speculate on what goes on inside a spider's head, but that there is something going on in there, I know better than to doubt; even had I been inclined otherwise, the actions of one spider over the span of a couple of evenings would have amply sufficed to disabuse me of the error.
Lest it be said I am ungenerous in my critique, I'll note that, overlooking the taxonomic confusion already discussed, your understanding of insect behavior is roughly on par with that of the naturalist Jean-Henri Fabré, whose writings on spider wasps were much celebrated in their day - which was roughly contemporaneous with the American Civil War. Much has been learned since, most of which Fabré has probably been unable to appreciate owing to his death in 1915. You and I are more fortunate. So if nothing else, it may be worth your while to take advantage of your luck, and pursue your study at least to within shouting distance of the present day before attempting to generalize.