One disagreement is technical: can developers provide communities with a safe, functional iteration of their servers to deploy freely in such a way that discontinued games continue to operate?
The answer is "probably not". The devs speaking out aren't wrong about this. This requires rebuilding the entire concept of server architecture for games and centralized servers. Not only are older games probably unsalvageable for that process, but any game that is buying online services would be priced out and you'd end up with only the largest publishers being able to afford basic features like, say, matchmaking.
I think a lot of the devs speaking out are missing the forest for the trees.
There are unquestionably technical challenges involved in having to release the server software for games. These aren't the days of Team Fortress 2, and a lot of multiplayer games require clusters and massive tech stacks to handle authentication, persistent storage, and cross play. Add on to that legal challenges like licensing of third-party software, and yeah, it's nearly impossible for a publisher to just release source code or an executable file for the server software.
Multi-player games being killed is an issue, but it's not the big issue that preservationists and consumers care about. The big issue is single player games being designed with the requirement that they connect to publisher servers for activation or for some multi-player component, then the publishers shut down the server and render the entire game inoperable. For example, I have an old CD copy of Bioshock for PC (a completely single player game) that I can't do fuck-all with unless I crack it, because it's tied to Games for Windows Live.
It's not reasonable to expect a developer to make their proprietary server code available after a game reaches end of life, and I absolutely agree with the devs on that point. It's more than reasonable to expect a developer to not be allowed to lock the entire game behind a limited-life service that isn't strictly required for it to be a playable game.