The killed products that I personally actually used were:
YouTube Originals
Google Chrome Apps
G Suite (Legacy Free Edition)
Material Gallery
Google Sites (Classic)
Google My Maps
Google Play Music (replaced by YouTube Music, which is a degraded experience I pay for but do not use as much)
Google+
Google URL Shortener
Google Goggles
Google Nexus
Picasa
Google Reader
I personally think 13 is a lot, but understand that's a matter of opinion. The quantity is less important than the quality, though. I relied on Google Reader, G Suite, Google My Maps, Google Play Music and Picasa. I know of businesses built on Google Chrome Apps, and purchased services from one of them.
Those particularly personally inconvenient ones made me understand that I was too reliant on Google products, any one of which could be yanked at any time for any reason or no reason: Gmail, Voice, Google Drive, Google Cloud Platform, YouTube, and now Google Domains.
I don't have insight into why some products get yanked and others do not, and came over time to understand that my internal model about it does not correspond to actual Google reality. For instance, I might think that Gmail is way too valuable a property for Google to ever kill, but I would have thought that about many of those others, too.