Shortest answer is that even if all Starlink satellites suddently exploded at the same time for no reason, they’d fall back to Earth in a matter of weeks. They’re waaaay lower than the other satellites you’re thinking of (see discussion on geo-stationary satellites for why), so they need to be actively pushed every few days just to stay up. They’re so low they’re still subject to atmospheric drag.

Search the web for “star link Kessler syndrome”. It’s well documented. It’s also discussed elsewhere in this thread.