This may be an answer to your title question more than to your follow-ups, because I want to slightly challenge your assumption that trends in literary production are automatically echoed by a certain kind of recognition in literary criticism. That is, there is a step that comes before the question of the general population's awareness of literary trends. Though it is true that we can (and, near-obsessively, do) retroactively identify certain phenomena as literary trends, movements, or periods, it's not clear to me that this means that criticism recognizes or follows these things in lockstep, in part because (elite academic) criticism as we currently understand it was more or less invented in the very late-nineteenth or early twentieth century.^1

My main area of research is in children's literature, which is actually a really interesting case study for this kind of question, because the degree to which books perceived to be for children are considered 'literature' - and therefore subject to criticism - turns out to be really historically contingent. The perceived acceptability of certain kinds of books for "serious" literary criticism is tied up not in the content of the book itself, but rather in a) the audience the book is assumed to be "for", and b) the existence of an apparatus that supports academic or elite literary criticism.

So using children's literature as an example, we can trace how actual books interact with their audiences of various sorts to produce, or not produce, criticism.

Beverly Lyon Clark's book Kiddie Lit: The Cultural Construction of Children's Literature in America considers the history of American children's literature in terms of its reception: that is, how critics, readers and librarians read, responded to and studied it over time. Clark argues that before the turn of the century and the institutionalization of literary studies, many of the books that we would today consider firmly within the category of children's literature were not so designated at all. Rather, books like Louisa May Alcott's Little Women and Frances Hodgson Burnett's Little Lord Fauntleroy were marketed to, read by, and assumed to be for men, women, and children equally.

However, to simplify slightly - not least because I don't have a copy of the book to hand - Clark argues that around the turn of the century there occurred a suite of changes vis-a-vis the cultural perception of childhood (including a general resistance to sentimentality, and a sense that America as a nation was metaphorically "growing up" into a robust, adult masculinity with no time for childish things) and a new interest in developing literary studies as a rigorous discipline to be pursued by serious academics in institutional settings. These broad changes led to the effective ghettoization of texts that were perceived to be childish, not robust, and not serious: in short, books that now seemed to be for women and children were excluded from the category of the "literary" altogether. (And don't even get me started on fantasy and - later - science fiction.)

During the early decades of modern institutional literary studies, then, scholars (who - does it need to be said? - were primarily white men) completely ignored huge swaths of very popular, vey timely, and often very innovative work because it was considered beneath their notice.

So, in fact, in some cases the general public may have a better idea of what is going on in certain branches of literature than does literary criticism, because literary criticism had a habit, through much of the twentieth century at the very least, of being deliberately obtuse about the true shape of the literary world. In other words, what is important about literature in general is not always the same as what has been important to the people who have written literary criticism.

This last point is edging up on the 20-year-rule, but I'm going to risk it because it's more of a meta-commentary: for the last few decades, one of the big tasks that literary studies has taken on is one of recovery and rediscovery. Whereas early institutional literary critics pruned down the list of writers and texts to the Old Dead White Dude canon, absent (most) women writers, absent children's literature, absent melodrama and sentimentality, absent genre texts (unless sufficiently literary in another way), there has been a significant push to use evidence such as circulation and publication runs to re-evaluate what constitutes "important" literature, to (maybe, partially, imperfectly) bring criticism a little better into alignment with the books that were actually read, loved, passed around and talked about amongst the general public.

^1 This is obviously not to say that no one wrote about books before that; but as an academic discipline that was housed in universities and regularized by university-trained professors rather than being done in popular magazines or other cultural fora, criticism emerged at around the turn of the century.

Edit: sentence streamlining