A self-improving intelligence can indeed be the Great Filter, that is, if it has already reached us from elsewhere, potentially long ago.

Keeping in mind that the delta between "seeing evidence of other civilizations in the sky" (= their light-speeded signals reaching us) and "being enveloped by another civilization from the sky" (= being reached by their near-light-speeded probes) is probably negligible (order of 10^3 years being conservative?).

Preventing us from seeing evidence, or from seeing anything at all which it doesn't want us to see, would be trivial.

Yes, I'm onto you.