RE: Is knowledge impossible, or is pragmatism sufficient?

I'm assuming by "knowledge" you mean "absolute knowledge". As opposed to a "relative knowledge" (="pragmatic" knowledge), which depend on assumptions/context/simplifications, that plays an important part in pragmatic applications (as you described).

The latter ("relative knowledge") has been both useful and sufficient for many applications.

The former is, at best, itself a special case of the latter. Where we say something like "Given these assumptions/context/simplifications this knowledge is absolute".

At worst, the former is a delusion. Historically, this type of "knowledge" has been "defended" less by reason, and more by ignorance or violence.