I think it's an entirely pointless exercise to argue that hockey of the past was "better" (whatever that means) than today, and it's equally pointless to argue that hockey of today is better than in the past.
I simply look at different eras as different eras. They're all more-or-less equal, though there are some notable periods where the talent pool was clearly extended beyond an ideal level (maybe c.1975 to 1979, for example). But even then, the NHL has always been the highest-level League on earth, so anyone or any team that excels in any era is deserving of high respect.
Fitness level of players, degree of 'hate' and competition between clubs, and entertainment value of the sport are all different aspects. Let's break those down:
Fitness is obviously a universal priority of the pro-player today, for a variety of reasons. Does this in itself make today's game/players better than in the past? I don't know. We all know the shifts have gotten shorter and the goons/enforcers are out of the sport, so that means all players have to skate hard in short stints on the ice. So, if you can't keep up with the pace, you can't make the NHL. (The lack of a red line also contributed to this, I think, as the 'stretch pass' is now the fastest way down the ice, whereas before 2005 everybody had to skate with the puck through the neutral zone.) But does everybody being super-fast in one direction mean the game is better? I guess it depends on how you appreciate the game. I like the super-fast pace, myself, but I prefer watching players stickhandle to stretch passes. Compare to baseball, for example. In baseball, not every player is expected to be a super-fast runner who can steal bases or beat the throw to first, and thirty years ago in the NHL not every player was expected to skate like Paul Coffey because players' roles on their teams were very different (and shifts were longer).
Degree of 'hate' and rivalry between teams is bad point of today's game, I think. Partly it's a result of the NHLPA being stronger than team-loyalty nowadays, and largely it's a result of money. Players are simply not willing to sacrifice their health or get 20-game suspensions, and coaches are smarter, too, and don't want stupid emotional plays that hurt their team. There's also much more awareness of health issues, esp. concussions. This is all good, and you can't really blame the players for it. But I think the NHL is partly to blame by being too slow to force rivalries. Divisional rivalries don't play one another enough now, or too infrequently. (I think last season, for example, the Oilers/Flames played on opening night and then not again until late January or something.) I personally think the bigger NHL now should be divided into two almost-separate Leagues, and that all the Canadian teams should form a division so that they all play one another a lot.
Entertainment value? I dunno. I thought hockey was getting boring (again) around 2009 to 2014 -- too low scoring, too much shot-blocking, too much defense-first with the game being coached to death. But for the past two or three seasons, it's been getting better and better. The old days of hate between teams may be gone, but the level of skill is strong now, scoring is going up, and the pace is fast.
