> Active debris removal (harpoon satellites, magnet arms, whatever) are not a solution to this problem and are a huge waste of money.
This is wrong because it's based on a flawed assumption.
That assumption being: Propellant is required to deorbit debris, and the rocket equation makes launching all that propellant prohibitively expensive.
And while we can't do anything about the rocket equation, we don't actually need to have propellant in space to deorbit things.
Ways to deorbit without propellant in space:
1. The ground based methods. Although these would likely be seen by superpowers as military escalation of the status-quo.
2. Propulsion-less drone satellites. All propulsion-less designs use some form of sail which can be used to change the drone's orbit to match the debris before latching on and towing it to a new orbit. Once the debris is now in a decaying or graveyard orbit, the drone can detach and go after it's next target. All that is needed is time, power (readily accessible via solar power this close to the sun), and reaction wheels (which now we know what caused previous designs to fail like in the Kepler mission, can be built to last).
The most common form of sails would be solar sails, but there's also EDTs and magnetic sails.