Here's my take. First off, there were way less players back then. The world was just starting to wake up to pool. The sheer number of players means a lot. That fact partially accounts for the fact that there is only one woman in the top 100 Fargo rankings—Siming Chen. In general, women are just not as interested in pool as men are. Secondly, the equipment was inferior. The cloth had a nap and was slow and the cues were spindly with lots of deflection. Today's modern low-deflection cues and fast, non-nap cloth allows smaller pockets. Just like golf, there is really no comparison between 35 years ago and now.
In a game like straight pool, with slow, napped cloth and needing to go into the rack multiple times per rack, Mosconi's high run is much more impressive than Jayson Shaw's. Sorry Jayson. You're one of my all-time favorite players, but that's the truth.
Here's an approximate analogy. I remember a Golf Digest article from the beginning of Tiger's career. Not to take anything away from Tiger, who I consider to be the greatest golfer of all time, but the article underscores the extreme difficulty of comparing athletes from different eras. In the 1967 U.S. Open at Baltusrol, with a final-round 3-shot lead, Nicklaus played safe off the tee with a 1-iron that plugged in the rough. He then chopped out with an 8-iron back to the fairway, leaving about 237 yards uphill into a stiff breeze. He then unleashed a famous 238-yard 1-iron, carrying the ball onto the putting surface, leaving a 22-foot birdie putt—one he rolled home to finish at 275, breaking Ben Hogan’s 72-hole U.S. Open record by one stroke. Golf Digest later recounted just how unforgiving that shot was: they brought Baltusrol’s reigning club champion, John Norton (no slouch by any means!!), out to hit Jack’s original 1-iron (and the same type of balata ball), and after 50 tries, he only managed one on-the-green. That single successful attempt underscores why Jack’s 1-iron that day is still talked about as one of the game’s all-time great approaches. Afterwards, Norton said the sweet spot on that 1-iron was the width of a dime. A dime! Today's golf clubs have a sweet spot an inch or more in width!
I submit that today's pool equipment is equivalent. Technology changes rapidly in a free market, which makes comparing different eras very difficult.