Sounds like my use case for Flickr differs a lot from the ones mentioned here. I don't store everything there (Over a terabyte of raw photos etc is not worth publishing;-), only photos I want to publish as an enthusiast photographer and see other photographers photos + talk about them. For that Flickr still trumps over 500px, Facebook* and any other service I've seen. Would've probably quit photography as a hobby multiple times without Flickr.

* Facebook is where other people are and there are some good groups but for really following other photographers it sucks + FB molesting JPEGs is just horrible.

I've been using 500px lately for my publicly available photos. Seems to be the most popular alternative.

For private stuff I am hosting the originals on my own NAS and upload a copy in Google Photos for easy searching.

Instagram. You can use hashtags to organize your photos similar to Lightroom and tag your friends to keep track of who's in them. I also found out if you use the hidden "Full Ten" filter it retains the original quality.

500px is apparently where all the cool kids go. I use Google Photos.

(500px has a really weird community. The hive mind likes photos edited to have a certain look, and there are lots of random people that show up to like your photos in the hope that you will like theirs, and they'll get popular enough to be featured on the front page. As a result, I don't use it. My friends on G+ are enough sharing for me :)