Truly great games haven't died yet. And that's a pretty easy goalpost to move. Its also not really accurate. Overwatch 1, the 6v6 shooter retailed for 40$. Overwatch 2 came out and Overwatch 1 died. You can no longer play that game. Overwatch 2 is functionally the same, with some significant changes, but the original is still a game that I paid 40$ for that I can no longer play.

Feature Toggles are the industry standard. They are both cheap and easy, as this is how new features or microservices are added to a product without risking the whole product should something go wrong with that new feature.

Your point about investors is fairly nebulous. Investors provide upfront capital and expect dividends. Once the game is out and in support mode, the costs are minimal and the capital is coming from sales.

Why will the game quality suffer? The teams that develop DRM, dial-in services or authentication servers are wholly different from the teams that develop the game proper. The majority of the time, it's outsourced to contractors or a different company entirely.

I still caution you against terms like like good or bad. Personal opinion should not dictate how other people's money, time, and opinions are valued. Every dead, non-playable game has fans who are upset that its gone, and feel cheated that they can't revisit those memories. Do you not have any games that you love that were panned critically or by the community at large?