I am quite well aware of these predictions that are made in general, but this is in an absurdly abstract model with patently false assumptions.

By 'this' do you mean the model of humans as perfectly rational agents? That's a caricature of microeconomics and is not necessary to make useful predictions based on microeconomic reasoning.

It predicts that, all else being equal, a rise in the price of a good or service will reduce demand for that good or service. Do you think that prediction is wrong?

No, I think it is trivial.

Maybe the simple fact is trivial but the implications are not. Microeconomic reasoning explains a number of facts that are non-obvious, counter-intuitive and non-trivial to many people, for example:

• Price ceilings cause shortages (rent-control, fuel price ceilings in the 70s).
• Price floors cause surpluses (agricultural subsidies, minimum wages increasing unemployment).
• Purchaser subsidies cause price increases (cheap student loans raise tuition fees, mortgage interest tax deductibility raises house prices).
• Low interest rates cause speculative asset bubbles and malinvestment.
• Banning the sale and purchase of drugs does not work and makes some criminals very wealthy.

If more politicians and voters understood these 'trivial' economic facts then we might see slightly better policy. Unlikely though, since politicians' behaviour is also best understood as a rational response to incentives.