"is everyone else in on some big game of pretend high cuisine?"

I'd say, yes.

I think there's two types of "expensive" (for lack of a better word). There's the type of "expensive" that does its best to have the surface appearance of quality, but under the hood it's all as cheap as possible. This is basically a way to con middle-class people by making it look higher class, but in reality, they're not getting that much more, so they can jack the price up a great deal more than the costs would require. (It's not entirely a con, in the sense that the customer is successfully projecting an image of a higher class wedding to their probably-middle-class attendees, but it's still an expensive process.)

Then there's the type of expensive where quality is actually a concern and the money is being put into improving the experience in a deep and meaningful way, tested by many people who have in some manner developed some amount of discrimination in taste by experience over years.

Signs you've got the former include: They're serving a nut/berry salad on a bed of mixed greens, because that's a sophisticated salad. But the sophistication of a nut/berry salad is the balancing of the bitterness of the nut against the sweetness of the dried berry (cherry, cranberry, etc), possibly helped by the dressing (most common with a bit more sweetness), and some of the greens (endive is a nice bitter, for instance). If you buy cheap nuts, they'll often have lost their bitter aromatics. Somehow, you can buy cheap dried fruit that isn't very sweet either. Or you can pair the cheap, not-bitter nuts with dried cranberries, so you're "balancing" bitter with sour, or bitter with "sour except covered over by too much sugar", or other such things. It has the form of a relatively sophisticated salad, but very little of the substance. Another mistake is treating the mixed greens as being all neutral, but including a frisee [1] in the mix, unbalanced. Frisee balanced with sweet is pretty nice; frisee left as the primary player in the dish is awful.

As you say, foods renowned for being tasty, somehow stripped of all taste. It is actually possible to serve a buffet of tasty food, but it is (no sarcasm) a challenge. It is certainly possible to serve plates of tasty food, even at a bit of scale. No sarcasm, at this point in my life I'd rather attend a wedding catered by Chipotle that a standard "we serve a fake-high-class fish and chicken plate with tasteless-pate and capers randomly thrown on things." The Chipotle will taste pretty good! (I actually thought for a while that capers were just useless signalling that nobody liked. Then I experimented and made a couple of home recipes that used them very well. They're still not my favorite, but I get them now, which I didn't after what must be several dozen dishes served with them present.)

The decorations of the hall are regular, mass-produced fittings, but someone came along afterwards and randomly sprayed them with something that looks vaguely like plaster.

The funny thing is that the price difference the two types of "expensive" are often poorly related, and at times they'll even be nearly equal. I know some restaurants where we end up with $25-$30/adult that are frankly only marginally better than Burger King. But I also know some restaurants with similarly-priced plates where all the food is noticeably a true cut above the common $10-15 places. But the former seems to have no problem staying in business. (At least in my area.)

[1]: https://en.wikipedia.org/wiki/Endive#/media/File:Friseesalat... possibly also known as "endive", though that seems to be a term for several varieties