Larger pockets and bad racking making the 9 on the break several times a match. Also cheap light ball sets. I saw some of the matches from ESPN and I would complain about that equipment in a pool hall as sub standard.
If you look at the average TPA, including what the pro pool announcers talk about, you used to be able to win tournaments with a .900+, now to win just a match you need to shoot like a .920 or .930. The standard for play is higher these days.
I love watching the older matches but I don't kid myself that the old school players could outshoot the modern group of guys day in and day out, the modern games just needs too much consistency to keep competitive.