I’m guessing that many of the “models” are somewhat sound in principle and theory (as far as that has progressed).
My contention is that they are filled with specious and BS assumptions - along with fake data, data sets with large omissions (ones that don’t support a desired outcome, etc.).
This is what Mann, Hansen and Jones were trying to do (and did).
Most of the computer models are built in reverse order. First you conclude that something is happening and then you construct equations and models that will reach that conclusion. When you find a flaw in the model, you alter it as necessary to keep the conclusion the same.
East Anglia University in the UK is the capital for climate science. Several years ago it was discovered in one of their equations that an element was off by a factor of 3000. That means 3000 times what it should have been. Six months later they came back with the equation fixed. Multiple variables were changed so that the answer stayed the same.