> The syntax and structure is clearly meant to try to mimic relatively natural language, yet in practice I think SQL is vastly more challenging and complex than most any programming language intended to be used by programmers.

I don't; and the fact that I've known plenty of people who are not programmers before and do not consider themselves such afterward who have picked up SQL fairly quickly seems consistent with it not being that much of a barrier.

I think SQL had some design decisions that are particularly frustrating to programmers who are familiar largely with currently popular general purpose languages, though.