There is no need to "open up Nostr to advertising." Nostr is entirely permissionless and anyone who wants to can advertise here. There's just very little value in doing so because the user-base is so small, and you can't target the advertising to make sure the users most likely to buy your product will see it.

That said, I do think it will be possible for content creators to make a living here. We need a few things to fall into place for that to be a reality, such as better content discovery, a variety of algorithms for users to choose from to surface content according to their preferences, and more clients that specialize in certain content formats. And, of course, we need more users for all of this to be sustainable long-term.