They don't ignore or neglect Half-Life, TF2, Counter-Strike or DOTA2. All these continue to receive updates (Half-Life just recently got a complete overhaul for its 25th anniversary and the other 3 are their bread and butter money makers and receive regular updates).
Only Portal, Richochet, Alien Swarm and L4D get ignored.
Don't quote me on these, but iirc, it was a Hearthstone and Magic competitor co-developed by Richard Garfield who is one of the two "inventors" of Magic. The game flopped hard, though, because the barrier of entry was too high by requiring an upfront purchase of the game in addition to booster packs which were outrageously expensive too. And the gameplay was also kinda bad.
Nah man. TF2 is unplayable outside of community servers because of all the cheaters and spinbots, and CS2 is just a CSGO update that killed community servers and removed a significant amount of content.
I mean they did do a lot of work for CS but at the end of the day only 1 of their 3 flagship multiplayer games are being properly taken care of