All of that has in fact nothing to do with Steam.
I think this conversation is going over your head.
What? There is no need to offensively end a discussion like that but if you want to...
You talked about the industry in your post. Steam/Valve is only the distributor. They don't decide or even influence which kinds of games were made (apart from the few they make themselves). That's totally up to the big publishers and not to Steam.
D:OS in fact proved that there is a demand for this kind of old-school isometric party RPG which hasn't be satisfied in the last years. But it's not Steam to blame for that, not at all. Also Steam's DRM policies have little to nothing to do with which games have been made in the past.
I think you're mixing up two distinct issues here...
Sorry, I mistook your response for being a TLDR, blah blah.... type of response to my points.
Steam is a distributor yes, but they enable the system and facilitate the control. The can provide digital distribution without facilitating DRM and proprietary mechanisms, they don't however by choice. So yes, they are part of the problem.
The control aspect is DRM. DRM doesn't exist to stop piracy (piracy proves this over and over), it is a means to shape and control the consumers to create more revenue channels (ie take something that costs the consumer nothing already and turn it into a service they pay for).
We used to own our games outright through the disks. Now they are digitally downloadable, but as you can see with Steam, Origin, and Uplay, there is a transition going on. With GoG, you can still claim you "own" the copy as you have it and can play it anywhere, install it anywhere, you choose.
With the others, you are leasing the game in most cases. You can only install as they allow on the things they allow and you have to be connected to their servers in order to play. Eventually, the shift of control will be to cloud computing, mainframe design where you no longer have a computer, but rather a dummy terminal and all of your processing is handled by them. This will open up more revenue streams such as charging per processing cycle, per bandwidth usage and per time to connect to services. When such happens it will be gladly done by the consumer base as they will rush off to chase the "convenience" aspect of it.
This is a long tirade, I know... my point as it concerns steam is a part of the industry they are a part of the problem.
Edit:
Oh, about your second point. I covered that in my previous comment. D:OS doing well doesn't disqualify my points. It actually proves it. The market was forced for a long time and it wasn't until Larian fought back, went out on their own and took the risks were they able to bring this to market, which as you said, people wanted. The market has been controlled for over a decade or more. All markets are to an extent.
