Flickr changed hands a couple times, almost went under and is still struggling to stay afloat. So you're right to be paranoid. I have been a paying Flickr Pro user since the beginning of time, but I don't feel that my photos are any 'safer' there than they would be on Google Photos.

Also, Flickr has done an arguably nastier bait and switch when they announced the end of their unlimited free storage. At least Google seems to be willing to keep the photos already uploaded around. For now.

I use Flickr as well but I also back up in other ways, including locally. As I wrote on another thread, I'd never depend on a photo sharing site as my primary storage.