Maybe I didn't do a good enough job demonstrating how common it is for backwards compatibility to be broken. You're right that many devs value stability—not just clojure devs. But there are also many communities where breaking stuff is normal. This is addressing the latter, obviously.
I'm sympathetic to this idea, but in practice it's very manageable. Function signatures destructure exactly the data that they need, so it's easy to tell what's required and what's optional.
Of course, normal rules apply like, "Don't pollute your program with a proliferation of booleans."