The problem is not not necessarily with the war dec mechanic itself.
It is a good thing that any player corp can declare war on any other player corp for any reason.
It’s rather how they are used (yes, there are exceptions and those are fine):
Mass deccing of random corps doesn’t lead to meaningful gameplay because neither side has incentive to do anything. The agressor doesn’t have to be aggressive and the defender has no need to defend anything. The result isn’t war (which was declared), but rather a legitimized, selective high-sec gate camp catching the unaware and unlucky while most people on the defender site keep doing their stuff with little to no interference at all.
The problem is based to some extend on the lack of ingame mechanics that can be reasonably used to pursue war targets. I guess, most of us agree that CCP should do something here that re-enables targeted war decs.
Another part of the problem is the shift in the game culture. It seems that players become lazier and less willing to invest time and effort into their content (in many areas of the game, not just the “merc” business): mass war decs became a thing even before the watchlist changes and the effort in picking war targets is non existant.
Broken is not that this can be done. Broken is that it seems to be “necessary” to do.
Ok, maybe not really necessary, because I’m pretty sure, if there would be some more effort put into choosing war targets, the aggressors would probably get the same amount of killmails with significantly less wars.
As I said above, there is simply no incentive to do so. But it’s the same for the attackers, no need to move out of the comfort zone where you can reship and ping for reinforcements. Sometimes, it happens nevertheless, which is a good thing, but people are normally rather risk averse.