Here's my analysis:

If an alien intelligence has reached Earth, it has technical capabilities at least a century ahead of ours.

Either (a) they do want to be seen by us, or (b) they don't care if we see them, or (c) they do not want to be seen by us.

For case (a), we would have unambiguously seen them by now.

For case (b), we would have unambiguously seen them by now.

For case (c), with their advanced technology, we'd never see them.

So... I very much doubt that an alien intelligence is here.