I think classic rock has more to do with the timeline and less to do with the actual quality of the music. They can't play something from the 00s and call it classic rock because it's less than 10-12 years old. But something from '91 (like the songs I mentioned) is considered to be classic because of its age.
The newer stuff will eventually get played on classic rock radio. Just probably not for another 8-10 years or so.