eeeCoD has way more widespread appeal + larger playerbase
You're completely right, but that only applies to post-CoD4. The series didn't becoming the gaming empire it is today during that games prime, but some time after. Whether or not that's obvious, I don't know. CoD4, on PC, had nowhere near as many total players as TF2 has or ever did have. I'm not sure if this matters, but they both released only months apart as well. So, despite having less total players, they still managed to have a bigger competitive scene, even with their North American scene, which was amazingly smaller than their EU scene from what I remember.
Why? My guess is because they played the game nearly identical to how the core game was played to begin with. They didn't have any class gimmicks or whatever. Sure, some weapons were banned and some weren't but were never used because others were a clear choice. Sure, some maps weren't ever in rotation. Either way, they managed to have a bigger overall competitive scene than us, despite having a smaller player count in general; there was absolutely zero support for the competitive scene from Infinity Ward.
My point is, developer support helps, but isn't the answer to everything. They make the games, but it's the community that determines whether or not the game stays alive and grows or dies. Well, at least in most cases. So, we're clearly not getting any 6v6 support from Valve other than a reminder on their website of upcoming LANs that aren't even on the front page. At this point, which is no different than any other point in our scene's history, it's up to us. We can either realize the game will never peak higher than it has in the past and let it ride out until its inevitable end, or we can continue doing our best to make the scene as good as it can get.
What was our record in terms of total Open teams? 60-64? Let's find some way to make it that again, or even make it higher, instead of discussing the end of something that isn't even over, and really doesn't have any right to be yet.