I"m not sure there is much that "WikiTree" should do. WikiTree, in the person of the Leaders, or some tech people, could, of course simply delete all files with a pre-1200 birth year. I don't think any proposal to do that is serious.
Beyond that, we are not talking about some entity comprised of others called WikiTree, but we are talking about we who are volunteers and members on this project. So I think a question framed in terms of what "we" can do would be more helpful.
I do notice in the discussion so far, some unhelpful absolutes. Everything could be deleted. All are bad, etc. The fact is there are real people with real documentation back there. William the Conqueror. Charlemagne. That's enough to eliminate the absolutes.
So the issue is not that they are ALL bad profiles, but there are SOME bad profiles. Yes. A LOT of bad profiles, imported by GEDCOM and never touched since. And because they went by different names, a lot of duplicate names that need to be cleaned up. And they need to be cleaned up by real people who are volunteers on WikiTree.
Which takes us to another issue. WikiTree is a collaborative site. Others have to be involved, and others have to be respected. That means WikiTree will never be a site like, say, Charles Cawley's Medieval Lands Database, which is a monumentally extensive work of one person -- and Ihave seen criticisim of Cawley's work because it is the work of one person. So one will never be free of criticism, but we choose the criticism of being the work of many people, and that means you can be 100% sure (and here I am using an absolute!) that even if only a very few of the world's top rated professional genealogists were allowed to work on pre-1200 profiles, even then you would find someone criticizing some profiles. So I think that's not an ideal we need to aspire to.
What we have now is a site that people know is highly variable in quality, and people will go to a profile and say, "that's crap" or go to another and say, "oh, this makes sense and has credible sources." I think it will always be good profiles that give WikiTree its reputation and not the opposite, Wikitree conferring a reputation on profiles. Profiles on any site really have to stand on their own merit, not the sites's.
I have spent the last several weeks on a rabbit hole that caught my attention sorting out some profiles in the 600s and 700s impacted by a legendary figure called Makhir. I certainly share with you the frustration of encountering profiles that are nonsense. But I take pleasure, as I'm sure you do as well, in trying to figure out what the sense is and improving the profiles.
In the process, I don't find the PMs the barrier that you do. Yes, there are a lot of PMs on pre-1500 profiles who are not pre-1500 certified, and if they don't want to become pre-1500 certified, then they really should take themselves off the profiles. [And this may be a real problem -- I suspect they no longer have access to the privacy setting to do that, so they are stuck in limbo.]
But the only thing you MUST have a profile manager or member of the trusted list to do is to merge a profile that is not PPP'd, and you can still merge a profile INTO a PPP"d profile if you're on the trusted list. And I've had no reluctance from profile managers in adding me to the trusted list. So I simply don't see current PMs to be the barrier that you do.
I've talked too long. The short answer is simply, "yes, there is indeed work to be done. And we are the ones to do it."