I've been watching games since the early 80s and seen more than my fair share of game tape from the 70s. Guys weren't chased around the ice after a clean hit back then. You'd take a number and hit back. The only exception would have been Semenko protecting Gretzky.
It crept in after 94 lockout, but didn't become standard operating procedure for teams until the last 20 years.
Um, you very much had reactions to hits like that. And yes, this very much existed way before the 94 lockout.
What you seem to be missing, is that there isnt some sort of standard. Player didn't adhere to one set of guidelines and then magically transformed and behaved completely different all of a sudden. Throughout times, sometimes players reacted to clean hits by defending their teammate and jumping the opponent, and sometimes by acknowledging that it was a clean hit and nothing needed to be done except perhaps dishing back some hits in turn. This has not changed one bit. Different people acted differently under different circumstances. Thats how it was in the 70s, 80s, 90s, 00s, 10s or the 20s. Players didn't have a magical understanding of a whole situation in the 70s, they were just as prone to judge any scene based on what they think they saw, and they reacted based on that. The main difference is that there were far fewer games on tv, and those that were, didn't have fans get ten replays from five different angles, meaning they had far less of a way to judge the scene as it actually played out.
As has been mentioned before, players don't have instant replay and slo-mo either. They react on instinct, not based on what is right or logical. What matters to them is how they perceive a situation to have played out. That, and only that, is what matters to them. And that is very much why reactions like from Kucherov (not so much the one from Geekie, those happened but have always been rare) have always existed. Players have always had limited view of what actually transpired, just like they have always been told to stick up for their teammates.
There was absolutely nothing out of the ordinary with what Kucherov did. Geekie, yes, but an immediate reaction to a hit, no, that has always been around. In hindsight, it may have been unnecessary, because the hit was clean, but Kucherov wasn't given hindsight, he was given his view of the incident, and a response based on emotion. Just like other players in thousands of cases over decades.
It's funny how we can have goal-reviews because no one was actually sure whether the puck went in or not, but god forbid a player reacts on how he perceived a hit. No, he must have perfect understanding of everything that happens on the ice at all times. It seems like some fans really have lost their touch in regard to understanding players and refs thanks to all the visual information they get, which is not available to those on the ice. It is completely impossible for players to always have the right idea about what happened close by, which is why you always have and always will see players show a reaction like Kucherov, even if having the full information shows it isn't warranted.
That doesn't excuse Geekie doing what he did a bit later on. Which is why he got a ton of penalties for it (see, the instigator at work, just as it was intended) and may get a fine or suspension on top of that.