I entirely agree that they need revenue - I wasn't saying that I shouldn't give anything back. What I give back is advertising revenue, by being willing to accept advertisements in return for the content. It's been how the Web has generally worked for years, and also supports TV channels and free newspapers etc. My worry is that because blocking ads is becoming so prevalent, this model is becoming uneconomical, and so that option is being taken away.
If they can offer subscriptions that provide more value, then that's great, absolutely, and something which I might well look into at those sites which I value most. I still have a subscription to a print magazine despite most if its articles being posted online, for one, because sometimes it's nice to read a print magazine. I also pay my TV license for the BBC, which I could legitimately opt out of because I watch next to no live TV, but I don't begrudge that considering the BBC content I consume. My concern is that casual browsing in return for advertisements will become increasingly less possible.
I'd be happy if the choice was either to accept ads or pay a subscription (maybe with some extra incentives), certainly. I just don't want the latter to start becoming the only option, as has started to become the case on some sites.