I guess where we differ is that I don't think those are content businesses. The OP was looking for alternatives to building a service or app, and those business

I guess where we differ is that I don't think those are content businesses. The OP was looking for alternatives to building a service or app, and those businesses are automated marketing systems. I think they're closer to apps than not. I took the OP's question to mean s/he wanted to create content.