[detaro]

It's a content container. A content container that for some of us is now stereotyped as "content in here is often low-quality", which means that in the vast amount of content on offer each day we're more likely to skip links leading to medium.com. If people regularly spread bad blogspot links around, blogspot would have the same reputation. (I'm sure there is tons of spam on blogspot, but when people share blogspot links in my circles they usually are blogs by people that have been at it for ages and care more about content than appearances, so for me blogspot is a high-quality signal)

Being in a known content container is great if you don't have your own "brand" and as long as people associate the container with good content. If they don't, or if your content is way above average, it pulls you down (which provides motivation for below-average writers to write on them, hiding in the crowd, and motivation for good writers to leave)