Rehab a Poor Performing Site

As long as you are willing to give it about a year to rebound and it doesn't have a trashed link profile, it's worth saving.

You could start building back links to your old content.

But I think you are making the right decision to start from scratch.

Here is what I would do:

1) Go to your Google Analytics
2) Remove all pages that do not receive at least 25 organic visitors per day

Start adding new content.

When people mention the word "fresh content", it is always that they think about of when they wrote it. Google doesn't care about that. What it cares about is "fresh backlinks". Google cares about the existence of, and the continuous persistence of backlinks. This indicates that random people make a conscious decision to backlink.

This "organic" nature of backlinks is what their algorithms are trying to spot. So you can even start "organically" backlinking your old content, and its traffic will start to grow. So, it really is a matter of choice.

I'd say that if some content was generated by robots, you're better off writing new content for this site.

I think the most important question, above all:

1) Do you care about this content?
2) Do you feel passionate about the subject of the site?

You know, it's not always about content, its how you feel about what you're doing. If you like writing about this subject, then keep on writing, create original ideas, try to shock people, or learn information that is hard to learn and teach it to them in your articles... create a following of people who dig what you are doing and can't wait for your next article.

This takes hard work. But if you are conditioned for being productive, then it shouldn't matter whether you are restoring an old site or starting a new one.

Hope this makes sense / or helps.