good points. In the beginning, I missed what you wanted to say, but it's true, manual blog comments that add value to the page you are commenting on work well, too.
As for web 2.0, this might be an unpopular opinion, but... I'm not a fan of nurturing web 2.0 websites anymore. If a web 2.0 website wants me to post content on it regularly, add images, format the content, make it unique and blah blah blah... basically, if the web 2.0 wants me to treat and nurture the website like it was my own in exchange for a backlink, but which can delete my account at the push of a button because of a mistake or because they feel like my services are not needed anymore, then I might as well invest my time and resources in creating my own PBN network, which gives me total control over my work and websites.
Web 2.0s used to work great for SEO in the past: you just created an account, slammed a PLR article on them and get a powerful backlink. Do this with 10-15 web 2.0s and rank. But nowadays it's more work involved and the worst part is, like I said, that you have no control over that content. If you're going to put your precious time and resources into something then put it in something that you own.