Disney is largely protecting its characters with trademark law now, yes. That's why there's no particular effort to extend copyright any further than they have.

Now, as long as there are companies in a capitalist system, or even in something closer to market socialism, trademark makes a certain amount of sense. You have certain branding that's associated with your company (even if it's a worker-owned co-op), and you don't want your customers confused over its use by another company. We can certainly think of ways the current system can be approved--wider protection for satire, or easier ways to shut down bullshit lawsuits without spending a lot of money--but the idea makes sense in this context.

Now, if we're aiming for a more commune-based system beyond market socialism, then no, we don't need trademark at all.