Sounds like a totally inefficient way to run a game studio. No wonder their output had dried up.something people don't seem to be aware of is that Valve isn't structured like other companies. Nobody at the top goes "okay let's all work on X" everyone works on things by consensus.
What employees work on is heavily influenced by the company's "employee review" system. Which is basically at the end of the year they decide which employees to sack based on reviews given by other employees. It's essentially a popularity contest. This directly influences what projects people work on because if you work on some big project by yourself you're likely going to get a worse review than if you work on a smaller one. This explains why TF2 kept getting random updates like Mann vs machine and why Valve seemingly prefers to keep updating older titles rather than work on newer ones. It's easier to work with like 2 other guys on an update that'll get you a better review than work on a game that won't be ready for a few years. Even if someone like Gabe Newell wanted to make a new Half-Life game, he couldn't just order people to do it they'd have to willingly congregate and work on it. And this has happened a few times but overwhelmingly what happens is the game will be worked on for a few years and then everyone will switch to some other project instead that they're more interested in. There have been several distinct versions of Half-Life 3 in some form of development over the past 10 years that we've only seen concept art of. This also happened to Team Fortress 2 where there were 3-4 distinct versions of the game with the final 07 version only being worked on for about 2 years. Despite the game originally being announced around 9 years prior.
This is also why the company has a relatively high turnaround and why a ton of "legendary" developers that used to work at the company left a long time ago. This system most likely worked just fine when the company was like 30 guys working on 1 game but it didn't scale to a company that now has hundreds of employees and dozens of active projects.