What is a dirt carrier network?

I work as a network engineer (technically I’m kind of a junior engineer, but I’m the only one we have) for a small ISP that peers with a handful of carriers and we have our own 10G dark fiber ring around Columbus, OH. One of our DF links is through Crown Castle, and we’re looking at getting another through them to a new office space in the next few months. We’ve been super happy with their DF and had little or no outages in my 2 and a half years with the company. Our CEO is looking at moving into the Pittsburgh area as well, and was asking CC about their offerings and footprint there, and they started trying to sell their bandwidth to us. I don’t know that we necessarily need it, but I don’t think it could hurt. I asked a network consultant that we use what he thought, and he said don’t buy bandwidth from them, their network is dirt. He’s said that or a variation of that (routes are dirt) before about a couple carriers, but I’ve never gotten a clear answer about what that means exactly. I looked at their BGP peers according to Hurricane’s looking glass and it looks like they have 3 direct peers. Is this what he means? If not, what would be considered a bad carrier network and why?