Neither Flickr's new 1000-photo limit on free accounts nor Tumblr's ban on adult content affect my accounts on either service. But Flickr's move has given me confidence in them, while Tumblr's move seems like they've just pulled the self-destruct lever.
My blog post on why: https://www.hyperborea.org/journal/2019/01/flickr-vs-tumblr/
(TL;DR: Flickr's customers are the paying users, and they're owned by a photo company. Tumblr's customers are the advertisers, and they're owned by a telecom giant.)