I think the last two things in bold are a big part of why things are the way they are.
There are no more career stopping losses, there are no more battlers retiring at their peak to pursue music. We don't want to let go of the top tiers that we like the most, and barring something drastic, we don't have to. If you ask me, the older guys are more dynamic, there was no farm system in place it was just a collection of the most compelling battle rap talent they could find. Math & Rex weren't even active battlers at the time, URL brought them back to battling. Cortez, Hollow & Verb were active, but when was X-Factor's last battle prior to URL? What about Young Miles?
We saw Shotgun Suge make a major comeback in 2015, and that was more important than any of the new guys flourishing. He's just a more interesting watch. K-Shine and DNA started taking battling serious again in 2015, and they were more entertaining than all the new guys. We want to see Qleen come back more than we want to see any of the newer guys. Truthfully some of us are more interested in Yung Ill somehow getting that old magic back than a new guy blowing up.