Despite the fact that Google proclaimed Picasa's retirement in early 2016, Picasa is still available, much to the relief of its multi-million user fan club. Like a detective who cannot retire while the villain is at large, Picasa sticks for now to harness your photo collections.
Available for both Mac and Windows, Picasa won't get new updates since Google has concentrated its efforts around its new Google Photos product.
In its glory days, Picasa was a head taller than most fellow free photo tools: it included a whole suite of decent camera effects (in pre-Instagram days, no less), it was fast, it offered facial recognition (artificial intelligence!), and made online photo storage a breath. Almost all of that is still available today, except for Picasa Web Albums (the online storage component), which was discontinued.
If you are still not impressed, there is plenty to like in Picasa including its excellent Fill Light tool to improve darker shots, the geotagging feature, the text overlay tool, and, of course, its impressively sophisticated blemish removal tool.
Picasa is a healthy alternative to most newer-generation photo editors / organizers. It's just a pity (and a shame!) that it's not going to be updated anymore.