You don't need Starship for limited constellations to cause issues with Earth based observations though. Also SpaceX isn't the only one that's going to be wanting to make a constellation.
Well in that case, we've had limited constellations that cause issues for Earth based observations for decades. (Note: this is one hint that the risk here is exaggerated... dealing with satellites has been a thing for a very, very long time. Filtering out satellite tracks is easy and common, and modern digital imaging and data storage techniques have made satellite track removal ever easier. And many satellites--particularly space stations--are orders of magnitude brighter than Starlink satellites will be.)