When I say that older great players could still be great today under tougher pocket sizes- I think that we all should understand that their mechanics would certainly need to be dialed in to a higher accuracy standard. The assumption that I have is that whatever made those guys champions years ago -- and now add into their routine the same training system that the greats of today have at their disposal-- the old-timers would certainly be greats of today as well.
Just pocketing balls accurately is one component of a world champion player. Guys like Greenleaf, Mosconi, Crane, Balsis, Miz, Varner, Sigel, etc., at their best, all had the make- up to adapt and compete in any era.
People say that there are many more great players at a very high level today, I often feel that way myself about the game today, but consider, this, all the old timers talked about thousands of rooms being open here in years past, and we always here about 100 ball runners populating many, many rooms in every big city during bygone years, yet guys like Crane and Mosconi and Caras still dominated for years! That tells you these guys had something very special when it came to playing the game and they rose above many, many very capable players in their time.