Google probably still uses PageRank internally but it's obviously trying hard to stay ahead of the game. SEO is kind of a detriment to Google rankings as it takes away Google's ability to rank pages authentically.
I think webmasters should focus on getting traffic from social media instead. It's difficult to keep chasing Google rankings when they keep changing the game all the time.
Trying hard to stay ahead of the game? Lol. They shared PR data publicly for over a decade. This is something they could have turned off at any moment. They kept it around because so many people were dumb enough to install the PR toolbar which gave Google tons of data on browsing habits.
With the popularity of Chrome, they no longer needed to rely on the PR Toolbar to get the same kind of info. In fact, I'm sure Chrome is giving them infinitely more data.
They never were sharing PR data as any kind of benefit to the community. It was 100% self-serving.
As for your advice on focusing on social media instead, that entirely depends on your line of business. A local dentist would be foolish to ignore SEO and focus on social media instead. Nobody is searching on Facebook for a dentist. They go to Google.
Yes, pagerank for public use (on your browser) is no longer available, but still used for Google internal use. Most SEO practitioners nowadays focus more on DA (Domain Authority) and PA (Page Authority) than PageRank. It's still a question for me why Google removed PageRank toolbar and make it RIP.
They turned it off because it no longer served a need for them. They provided it so they could spy on what people were doing online. It gave them lots of data to use. Chrome gives them way more data because it has a lot more users than the Toolbar ever did. The Toolbar simply outlived its usefulness.