The system is incomprehensible complex and unknowable, but it’s probably correct and can’t be improved.

What about new tax proposals? Shouldn’t we then reject them all to avoid butterfly effects in this carefully tuned ideal?

No one said it can't be improved.

I'm noting that our political system seems to generate lots of folks going "this is wasteful spending!" when it's… not.

That results in challenges in determining what's a "bad tax" and what's a "good tax", and the consequences of cutting programs may take time to show up.