They read The Three Body problem
Theres no hiding that fact. If they're within about 100 light years they'll be watching the effects of the Industrial Revolution on the atmosphere. Even if they're don't know the exact cause the spectra of pollutants and rates of change will give hints the changes are unlikely to be from random natural processes.
Outside of 100 light years but pretty much anywhere in the galaxy (assuming interferometers capable of getting spectra of Earth) will know there's some sort of life here. Even if you want to assume some aliens don't recognize life as we understand it they'll at least see extremely interesting and varied chemistry.
The idea you're going to hide Earth's biosignatures is silly. Trying to hide our technology signatures is pointless. At about 70 light years any interested aliens will start seeing isotopes resulting from above ground nuclear testing.
While telescopes indeed are not magic, an alien species at least as advanced as us could have telescopes capable of not only finding Earth but gathering spectra from it. It's certainly no guarantee Earth would be found but there's no hiding from anyone looking. There's no masking the chemistry of life on Earth and likewise no masting techno-signatures in the atmosphere.
The number of techniques for detecting exoplanets makes the Dark Forest concept silly. There's no hiding our solar system from alien observation. For dedicated observers (at the right distances) there's no hiding the existence of life, the Industrial Revolution, or above ground nuclear testing.