Overall talent is not not down, the average athlete in 2017 is stronger, faster, bigger etc. compared to the average athletes of previous generations. Go watch a game from the early 90's, its a lot slower then the game now a days.
The big difference is parity, you have a system set up now where it is very hard to have many elite players on one team, and you dont have many teams that are awful. This in addition to larger goalie equipment, more of an emphasis on D, and many other factors are the reason why guys are not scoring like that anymore.
Just one example, look at Mark Messier. As a kid, I can remember him always scoring that wrist shot while coming down the right side (at least that's what I remember). I feel that now a days that shot would never go in.