I was going off the OP post in the quote. The day of running a pile of sites alone is over IMO. I can manage a fair number but no were close to the numbers I was.
I agree that you can really can't properly manage 10+ sites. No doubt about it. At least not alone.
The reason why I did it was because I never ranked well for particular keywords and found blog as a quick way to get instant traffic for a keyword. For some reason, Google loves blogs. I could make a blog article and have it appear in search results in 48 hours. I never hard that luck writing content to a shopping cart.
Sort of like if I owned an electronic eCommerce shop where I sold tvs, microwaves, toasters, dvd players, etc. Let's say the store ranked well for "buy electronics" or "electronics online" but ranked poorly for "microwaves" or "buy microwaves" even on my category page for microwaves. Google just did not give it any juice for that.
So, I'd create a blog all about microwaves, how to buy them, where to find them and use that to drive microwave customers to my electronics shop via banners or click here links.
The idea wasn't my own. I actually stole it from two of my competitors who were grabbing customers I could have. So, I did it. For years, it worked. In fact, some of these sites still rank well today and bring in traffic but some are totally neglected by Google. I mean, I search for the target keyword... nothing. If I copy and paste a paragraph of article content and search for it in Google using parentheses, Google will show the article in its results. So I know Google still recognizes the site and it's content but just do not respect it (if that is the right term).
I wouldn't say the content on the blog is necessary keyword stuffing either, as much as gibberish that was probably written by content spinning or generating tools. It doesn't sound natural at all.
I feel like the sites that are still showing up in search results especially for target keywords, should be left alone if Google still finds time to crawl them. As far as the other blogs not ranking, my concern now is thousands of 404 errors along with just walking away from a domain that is 7+ years old. They say domain age is key, but I don't know why I let it bother me considering that I have had other sites rank after months of launching.