Why are you even continuing this conversation. They've already decided that everyone else agrees with them. No amount of responses from you is going to convince them otherwise. As for forcing co-op in this game. I play co-op in this game all the time both with my clan as well as pubs. The reason I do that is if even if I get teams who have no idea what they're doing I can carry them through, it'll just take longer. If they start going in a direction that forces co-op and makes it a compulsary part of the the game I'd just move on to something else.
Furthermore I really enjoy the core gameplay loop. The only thing in warframe that I'm currently not a big fan of is nightwave, other than that there are very few things I'd change.