Obi Toppin was 22 when drafted last year. I think it's just the glut of early entries, but I don't think it's that teams won't take older guys, I think it's just so many guys are leaving early, it skews the results away from seniors. For top kids, I think they see it as an insult to their ability to wait. But, I think he clearly needs to show more for him to be a top (first half of first rd) pick, and has nothing to do with his age. I think he'd be more likely to get picked in the first round next year, IF he comes back and demonstrated a decent jumper.
And Payton Pritchard. And Udoka Azubuike. And Malchi Flynn. And Desmond Bane. But yes, TJD needs to develop a mid-range and right hand before worrying about being a 1st round pick, aged 22 or not.