If you want to share photos in a social media sandbox, then Flickr is still a viable platform.
If you want to share photos on the web and just need a hosting, Flickr still satisfies this, and quite well.
Now if you simply don't like their Terms of Service and want to leave, then I don't know what options exist out there with the same type of interaction as Flickr aside from 500px. I paid for 500px for a year, and never went back. There really wasn't much in 500px that I wasn't getting from Flickr in terms of user interaction. As far as hosting photos, 500px didn't offer me anything either.
I still use Flickr, but very sparingly. I use it more to share photos on the web while still maintaining copyright control (e.g. posting on flickr doesn't give flickr rights to use your photos royalty free, like with FB or Instagram). But even then, I have my blog (VPS hosted on Linode) and my Zenfolio account.