First that's just star systems within 100 lightyears of Earth, systems with one of more gravitationally bound stars in them. There are thousands of stars within 100 light years of Earth. Most are red dwarfs but there's about a thousand F, G, and K class stars.[0]

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.

[0] https://chview.nova.org/solcom/stars.htm