Yes I know, I've heard that a lot and it's a weak and harmful comment that kernel people should absolutely not be making. It actually pains me to see it typed again. You don't actually want a software project to be like that, it makes it very difficult to enforce the license when it actually needs to be enforced because you can't get consensus from all the copyright holders. It also increases the risk that some copyright holder (like one of those descendents) goes rogue and you have another Patrick McHardy situation.
If there really was enough reason and will to do it, they would just track down those people, or they would remove that code and replace it with something else. Just like they've done every time in the past when there was copyright problems. Just like any other big open source project has done when licensing became a problem.
It might or might not be a good idea in general to not have a centralized copyright holder entity, but at least it cuts down on the humongous license flame wars, which, incidentally, is what you would get if you actually wanted to go through with an endeavor such as you describe.
Anyway, what Linux developers might be afraid of can not be mitigated by simply switching to an MIT license. What would happen is basically some modern variant of this:
If there really was enough reason and will to do it, they would just track down those people, or they would remove that code and replace it with something else. Just like they've done every time in the past when there was copyright problems. Just like any other big open source project has done when licensing became a problem.