Even more basic than that, why do we think radio/photons are the most efficient/effective way to communicate for an advanced civilization? Why would they be using them in the first place?

We already know neutrinos can travel through most mass, so modulating those would let you transmit through the Earth and Sun with lower latency and without a repeater constellation routing around the object.

Whatever aliens might be using to transmit information is likely more advanced than we're able to detect.

Yes, that's another example of tuning the parameter-space for a possible answer, just an unlikely one. Yes, maybe the Milky Way is just chock full of highly advanced technological species who have all made themselves very hard to detect and none of whom have any interest in communications with other intelligent life.

But a simpler explanation that has many more paths to being true is "there's nothing out there."

To be clear, I don't think the evidence suggests near-certainty here. I wouldn't say that there's a 99% chance that we're alone in the galaxy. But it's also not a wide open field. There is some evidence, and so far that evidence suggests that we're likely alone.

I think your assumptions about what is hard and what is easy to detect need some recalibrating.

Alien life forms wouldn't need to use technology to make themselves harder to detect. It's extremely difficult by default.

They would need to use technology to deliberately spread a message in a way that is at all likely to be detectable, and even then would still have to get quite lucky.

Encrypted data does not look like noise. It looks very very different from noise. If not, the entire concept of communications engineering wouldn't exist. We're always looking for the next sharply bounded filter.

Well, that should be just temporary before our real mega engineering projects get started. Hard to not notice those, even just by the expected heat signatures.