NFL isn't dependent on RSN's. College football and basketball aren't either. MLB, NBA, NHL are. I guess they all hurt a bit when ESPN loses subscribers, but streaming services offer ESPN.
Now, I forget if it was the write-up in Fangraphs or BP (both were good), but it was pointed out this doesn't mean the RSN model is dead and kaput. It was a mismanaged situation by Sinclair/Diamond and they just racked up too much debt on the deal they couldn't stay afloat. This does not mean an RSN can't be profitable, but it certainly isn't the cash cow it was 15-20 years ago.
The cable model revolves around bundling and making sure people are paying for stuff they don't watch. Not everybody is a sports fan, but every cable subscriber has ESPN. Every cable subscriber has Fox News and MSNBC, although I doubt there is anybody who watches both at this point.