This is a poor comparison. The contrast of a cars to the background of Earth is low, ofcourse we can not see any. Remove Earth and let these cars fly on orbits 500km below ISS and, oh boy, would you suddenly see car roofs and windows glinting in the dark everywhere.

Amazing for satellite watchers and annoying for astronomers were e.g. Iridium flares. See [0][1]. Worst case for Iridium flares was them being about 50x as bright as planet Venus. Starlink satellites have the advantage of orbiting far lower which puts them into Earth's shadow on part of their orbits. Around midsummer, though, satellites in an orbit at 550km, like Starlink's lowest shells, will be lit by sunlight as soon as they cross northwards over ~ 45° latitude (their orbits have an inclination of 53°, so they definitely do this). I'm going out on a limb here but they might interfere with infrared observations because of emitted heat (being exposed to bright sunlight every half orbit heats them up).

Parent poster was most likely also referring to the Kessler Syndrome [2] when talking about safety.

[0] https://youtu.be/MTGVuPr9Epg?t=100

[1] https://en.wikipedia.org/wiki/Satellite_flare#Iridium_flares

[2] https://en.wikipedia.org/wiki/Kessler_syndrome

> and let these cars fly on orbits 500km below ISS

I understand the point you are trying to make, but the ISS orbits at an average height of only 400 km.

What percentage of the sky do you envision will be occupied by man made objects?

Very small, but that's not a useful measure. For astronomy, remember that bright, fast-moving objects will leave sizable streaks in images that halo a lot[1]. OTOH, intensity varies with time and satellite height. With regards to how much space we have, note that a satellite is taking up an orbit, not a point, and it's a lot harder to fit things in those safely, since they have a tendency to overlap.

[1]: https://nationalastro.org/news/starlink-satellites-imaged-fr...

To put this question into perspective:

The Iridium flare which you saw in video [0] so nicely next to what looked like a full-moon was produced by a flat, reflective surface of less than 2m² area at a distance of over 600km. Percentage does not matter here.