I think Valve's flat structure strategy has mildly failed and they should try something else. Unless they still desire to all-in on the strategy of creating products and hoping to land a another billion dollar baby, then sure, this strategy is good for that. However Valve kind of advertises itself as a video game company, and if someone is interested in making video games I feel like they'd actually be a bit disappointed after a while of working at Valve, simply because it seems so unlikely for them to actually ever release a video game.
And the bonus structure that I recall also seems dated. iirc it was setup in a way such that delivering new projects would land you a bonus. But this incentivizes creating things, but there is no incentive to continue supporting or updating or iterating on it. In my opinion the bonus structure should be done in such a way so that if you deliver something new, you would land a bonus, and then you'd get larger bonuses at the 1 year mark, 2 year mark, etc, if that thing has been updated and improved.
Many things these days are not just a single product that you release and that's that. They continually live on, they're a service, they're interacted with for years. Valve has fallen behind in this regard. Even smaller things like mini-features in Dota 2 for example would be released, which likely earned someone a small bonus, then left by the wayside to fall apart.
I love Valve conceptually but I really wish they'd iterate on their company design instead of thinking they've "solved it" I guess. I wish they were more video game focused. Obviously I don't know how it actually is in there these days, but things like this manual and other hearsay / rumors are the best I have to go off of.
From a purely financial perspective, they SHOULD continue to focus on marketplace dominance via STEAM. Whatever game is made for HL3/TF3 will ultimately fail to meet fan expectations (Duke Nukem anyone?).
They have however refocused on cash-cow live-service games rather than the polished single player experiences they were originally famous for. In the 13 years since Portal 2 they've only released one single player game, and that one was driven by their company-wide VR push more than anything else. It's harder to get excited about their games when they no longer want to make anything that can't be leveraged into an infinite money siphon.
They've also had an uptick in disastrous flops with Artifact and Underlords, hopefully Deadlock will be a return to form.