I've been a Smugmug user for many years. I also had a Flickr account from the very beginning, but kind of abandoned it. I was shocked when I first read that Smugmug would be taking over Flickr. My first thought was, "why would you buy a platform whose time has passed?" I know they said they didn't acquire Flickr because it was a golden opportunity, but of course they hoped to revive it enough to keep it sustainable and thriving. There is something to be said for saving and maintaining the vast archive of photos on Flickr.
Personally I think Flickr is a much better photo sharing network than Instagram or Facebook. Instagram looks terrible on anything other than a smartphone, and it crops your photos if they don't match their limited aspect ratio set. At least Facebook displays higher resolution photos in whatever aspect ratio you want, and works on all devices. The issue of course is that Instragram and Facebook are where the most people are. Nobody is going to convince longtime Facebook and IG users that they need to switch to something better (even Google failed at that attempt), but maybe the younger people who avoid FB and IG can be convinced. Then again that demographic is more mesmerized by the fleeting nature of Snapchat and TikTok (they've probably moved on from those as well, but I'm too old to know).
Smugmug has at least carved out a nice niche of serving photography enthusiasts and professionals. Their service still appeals to the likes of me, but I hope they can survive cutting their losses with Flickr if they can't make it sustainable. Makes me kind of want to create a new premium Flickr account just to support them, but I already pay for a Smugmug Power-Plan account.