dqzGuvenwith major updates still being released by a developer team who cares
While I can appreciate this the most, I still don't see how TF2C gains traction with the current competitive community, where people are pretty much used to the 2017+ version of the game. Making a fork of 2008 TF2 and adding a bunch of custom mechanics, weapons and gamemodes on top of that just doesn't seem like something you would play instead of what we already have.
People generally welcome improvements to existing maps, rulesets, server and gameplay plugins in current TF2, but with this you may as well be offering to play some other game. If it's meant to not be taken too seriously, then sure, maybe some people would be interested in playing a spinoff TF2C cup, similar to how ultiduo or mge cups are played now.
I agree that this is not necessarily something to choose over live TF2 and replace it; and it is not a "better" or "worse" TF2 either, it is just something different. But I don't think its potential is limited to being a fun cup either. Not necessarily. Initially it may start that way, as Highlander did and hung around that way for 2 years before breaking through. Although the accumulated meta and legacy now is almost 2 decades' worth, and the habits are even more rooted, I still trust the fun and variety TF2C offers. Not as something that will "steal" live TF2's player base by the way, but as something that will co-exist amongst others, as 9v9 co-exists with 6v6 and enriches the TF2 scene.
If it indeed stays forever as an event-based, occasional thing as you said, personally, that is also fine by me. This is a very personal thought though, and does not reflect the community I am in, or other communities gathered around TF2C.