Source Memes

Half Life recently got an installment with Alyx, and just got a free remaster 25 years after release, with the whole non-VR franchise is perfectly playable for dirt cheap on any old system. Portal has received spin-offs. Team Fortress isn't getting the attention it deserves, but is perfectly playable on modern PCs and has aged like fine wine while receiving bugfixes and new community-made, Valve-approved content every so often. Afaik Dota 2 still has an actively supported pro league. CS got an overhaul, for better or worse.

Valve is unique in that they are one of the few developers that understand that sometimes you don't try to fix what ain't broke-- this is why TF2 outlived Overwatch, and will almost certainly outlive Overwatch 2 as it has many other games.

Valve doesn't hold out on releases out of intentional neglect, but are instead painfully aware of how hard it is to meet growing expectations and continue to improve on what many would already consider to be near perfection. That's why we don't have HL3.