The thing with the argument that we traded Zucc, Hayes, Nash, McDonagh, etc so we might as well trade Kreider too is that those were all needed things because at those times we desperately needed young assets that we got in return.
At this point, there's a legitimate question as to what this organization needs more between more young assets/picks and established veteran top 6 forwards who provide leadership and stability.
Without Kreider and with Strome and Fast in question, the only experienced players in the entire forward group are Panarin who has been in NY a year, Mika, and Buchnevich who doesn't really seem to be a leader by any means. At some point you have to ask yourself if you're teetering on the edge of an Oilers type tear down where you tear down too deep, try to backfill leadership with UFA retread who have no experience in your organization, and you end up with a bunch of talented kids trying to swim in the deep end all alone.
There is nobody to replace Kreider either from an on-ice perspective or from a leadership perspective. People saying Kakko can replace Kreider on ice are really reducing both guys down. Both are big guys who play some kind of power forward game, but Kakko isn't a net front player like Kreider is and even though his skating will definitely improve, he'll almost certainly never have Kreider's speed to push D back. Those are probably the two biggest parts of Kreider's game. Leadership wise, there's more to it than being a supportive person or someone who can rally the guys behind you. A team also needs some leaders who are comfortable and established within the organization, which Kreider and very few other guys left are. It's hard to go to someone for support when they're just getting comfortable themselves.
So, yeah we did move a ton of veterans that people were attached to and it did end up being beneficial, but the team today isn't the same team the those guys were taken off of. There's real reasons to doubt that trading Kreider will be beneficial.
