I mean if we just don't believe in the institutions anymore why would we even care about what the Founders thought or would think?
I care because I want to look critically at what they did and use the parts that make sense, and I want to know what they thought about both those parts as well as the other parts so I can more easily learn from it. Not enough to spend a lot of time reading about it, though, so obviously I don't care personally and only in principle. Every so often I go off on a tear about some particular subject and learn about what they thought about that, but it's not a hobby.
What matters more than what they did is what we need to do now. This is a different time. We should probably do many things differently. This first past the post voting thing is bananas, as is the undemocratic system of not counting our votes for president individually.