That’s just not true at all. There are many universities and companies working on prototype satellites using many methods to attempt to deorbit space debris. We are actively researching right now because it is such a problem.
https://www.space.com/35543-space-junk-japan-tether-experiment-space-station-htv.html (Failed, but that’s space)
You have the guys from Surrey from the article Bentware posted.
Another satellite was just or about to be launched that will be testing 3 different methods of capturing debris. I don’t know if that’s from Surrey or another one I heard about.
On top of all that, we don’t have the proper research done to allow such a scale of RPO(Rendezvous and proximity operations) to be done. If we send up 500 satellites how do we have them report their constantly maneuvering positions to avoid collisions with other satellites? Who do they report to?
Before you can have the necessary hundreds to thousands of satellites you need rules of the road that are only being established now.
https://www.darpa.mil/news-events/2017-10-04 For the record, on orbit servicing can be refueling, repairing, or deorbiting space craft and debris.
I can assure you the problem is being taken very seriously in the space community.
This is also not true. The way Gravity portrayed orbital mechanics was 100% wrong.
When the US tested their ASAT missile it was on a LEO sat. Most if not all of the debris from that event has already deorbited. Debris tends to stay where it is. A collision in GEO will not effect LEO in any way and vice versa. Under ~-600-700km Altitude the debris will deorbit ‘relatively’ (A decade or two) quickly. The rest is pretty permanent.
You can definitely have those events that lead to a snowball effect that essentially destroy an entire orbit, but for the most part it will be just that orbit.