I don't believe this to be true. Back in the late 1980's, at the majors, Strickland, Sigel, Varner, Hall, Reyes and Archer dominated as a group. There were few Cinderella stories at the majors comparable to last year's Spanish Open, in which Jinhu Dang and Marc Bijsterbosch found themselves in the final.
For every super-straight shooter at 9ball back then, there are five today, and they are doing it on much tighter equipment. So, yes, in my opinion today's players are much better than their counterparts of yesteryear. In defensive play, however, I think the two best players of all time were Reyes and Varner, and I feel that in the current generation of players, only Pagulayan is in the conversation with them for best-ever defensive player.
That said, one's greatness can only be measured by performance against one's contemporaries. Who is best at 9ball between Lassiter, Sigel, Varner, Gorst and Filler? The question is unanswerable. Each frequently prevailed against fields they faced and all are rightly viewed as having attained the highest possible level.