They want to change it because they are sick of the image of the NHL being one where people try and kill each other. And no, Gretzky was not a tough gritty player. Gretzky and Shanny weren't even remotely similar players on the ice. Everything else you said is ridiculous hyperbole. No not every penalty should be a suspension, but when the NHL makes rules about wanting guys to not target the head of other's due to scientific evidence of repeated brain trauma leading to death you should expect the players to follow the damn rules. None of the suspensions handed out by Shanahan have been on questionable hits. Not a single one. Every single one has been on an unnecessary boarding or a unnecessary shot to the head. There have been a couple non-suspensions that didn't make sense, but for the most part every action the NHL has made on discipline this year perfectly matches what the NHL is trying to change about the league. They simply don't want you to target the head because it is a serious injury risk compared to hitting players in other locations.
Personally I could care less if they got rid of fighting or kept it in. It doesn't serve a purpose in the modern NHL anyways. There are only two situations in which people even fight anymore, either if someone from the opposing team makes a questionable hit on one of their teammates or if their team is getting killed and they need "motivation." I am not a big fan of NHL teams having a roster spot reserved for the fighting goon who serves no other purpose than to come on the ice and fight, like Boogaard for example who scored THREE times in six NHL seasons. Guys like that have no business on NHL rosters. You can have tough, gritty players that also serve as a functional player on your team like Lucic, Darren McCarty, Claude Lemieux, Domi, etc.
But hey, to each their own. I enjoy my hockey to be more of the open European style with enough tough play to serve a purpose and you enjoy the 70s style Flyers play. The NHL is going to go in the direction it wants to regardless of what any of us think.