Overwhelmingly their target base is women. If you look at their newer markets around the world, uptake is always dominated by that demographic. Pinterest doesn't release very detailed information on their user demograhpics, however I'd be surprised if it's not 2/3 women or greater.
I entirely agree with the annoyance of the Pinterest image mess in Google image search results, which has been going on for many years now. However there is a legitimate place for Pinterest in terms of what it does. The parent should primarily be annoyed with Google (which is intentionally - they're fully aware of what's going on - filling their image results with Pinterest images), not Pinterest.
I can't use it because of it's closed nature, but it has a very good set of image cataloging and sharing features. Add in the valuable network effects and I see why people use it for idea sharing/collaboration.
I understand frustration of Google image search users. But pins in google search results are Google's problem. I switched to DDG myself, and find it more straightforward for keyword based image search.
Their image related grouping works way better for the things I'm interested in (art/illustrations) than other sites.