The first 3-6 months of 2000 had
Goldberg: Out injured
Sting: Out basically until mid March
Hogan: Feuding with Lex and Flair (for the 80th time)
Nash: Out hurt from Feb-June
DDP: Randomly took 2 months off despite not being injured
Flair: Feuding with Hogan, being Lex's stooge
Savage: Had been out of the company since August of 1999
Hall: Injured in Feb, never to return
Bret: Injured in December, made it less than 2 weeks into January never to return
Sid: Stuck filling in for Goldberg and Benoit at different times, then repeatedly jobbing to Jeff Jarrett, then kicked to the curb with the reboot
Luger: Feuding with Hogan and Sting who wasn't even around for 3 months of the feud
Booker: Not a main eventer until the middle of the year
Jeff Jarrett: He's fukking Jeff Jarrett
Scott Steiner: Didn't actually get to the main event until November
So what you were really left with was Jeff Jarrett, Booker T, and a few 40/50 year olds that were done putting in effort. Meanwhile, WWE had Austin/Rock/HHH/Angle/Taker/Benoit, plus a bunch of upper mid carders that could plug in when need be, almost all of which were still in their 20s and the oldest guy on the roster was Austin, who was 36.