I don't buy the idea that Maryland football can never be a legit top 10 / top 15 caliber program, and a perennial top 25. Maryland is the biggest college and biggest college program right in the heart of a large market.
I think they'll need to find a way to lure a legit, "name" head coach with a top tier track record at some point. Someone that had big success at a big school for a while, then maybe got the boot because they failed to live up to elevated standards. That sort of situation...
About the closest MD got to that was when they almost hired Mike Leach, and you can debate whether or not he had big success at Texas Tech.
I think their ceiling is significantly better than where they sit right now. I don't know that it's legit Top 10-15, but being somewhere in the Top 25 at the end of a season is not much to ask. But as a bottom-tier Power Five program like they are now (at least when it comes to results), they are likely going to have to be able to identify a candidate who doesn't have the sort of track record you'd ideally like to have when you are committing tens of millions in salary.
It's obviously not an exact science to get a coaching hire right, but MD has had far more failures in that department than successes.