I think part of the backlash is coming from developers on web-applications that have business models that require scaling to very large loads before they make sense. This puts a premium on keeping things very cheap (no heavy commercial SQLDBMS), and inherently scalable (hierarchical).

Web developers on these types of projects cannot either a: buy a "real" SQLDBMS, or b: charge their customers so their business model makes sense without a huge number of transactions. This means they are willing to suffer it out with solutions that don't provide flexibility or data correctness guarantees of a RDBMS.

This is just a guess, but it's quite likely that it is the rise of hyper-scale-intensive, speed-intensive, revenue-light business models that drives devs towards deciding SQL isn't worth it.