The problem is the debris can easily take things out at sizes of a single bolt, given enough speed and an unlucky hit. You can't really blow it up. As it is, we're very rapidly approaching a situation where garbage collection needs to take place. But like every other example of "tragedy of the commons" everywhere, nobody wants to bother doing it.

Basically, magnets are great... for the parts that would be magnetic. But many are not. And there's not going to be some universal attractor we can just throw out there. Meaning to some extent you have to go and pick shit up manually, like with large nets (which is impossible for paint flecks and whatnot, which nonetheless travel at such speeds as to cause damage). Only instead of trash cleanup in the oceans, it's inconceivably more expensive, and more difficult. There's a reason people have been pointing out that we have a problem. It's a big problem. One that's only getting bigger.

Generic wikipedia overview for the lazy