Unfortunately not all websites can you receive a backlink from that will directly benefit your website. Some websites, like the ones you mentioned, may be difficult to link to your own website. This may either be because they do not allow you direct link to your website or if they do, it has a "nofollow" tag associated with the link. This means that it will not be indexed with search engines.
Don't fret though!
Writing Hubs is a great way to link to your websites. Just make sure you have a high Hub score for each Hub (I believe it needs to be above a 60) and your profile score is high as well.