Link: https://nitter.net/TeamFortressS2/status/1745157814295617767
Valve is generally supportive of mods (hell, a Portal 2 mod was just released a few days ago) but it seems like recreating Team Fortress 2 was pushing it… Really sad, honestly. I really hope Valve would just strike a deal with these devs and make it official rather than throw away the insane amount of effort they put into re-building TF2.
They most certainly made a decision based on priorities and TF2 wasn’t a big enough one for them to jump on. If there were enough users who would pay clamoring for it, they’d move.