Do we still need journals?
I argue that we don't. Authors can easily self publish for very low cost. The traditional journal actually limits the value of peer review by restricting it to a few arbitrarily chosen gatekeepers with limited skills and perspectives, while open post-publication review allows a large number of reviewers with diverse skills and perspectives to participate. The shorthand of impact factor and journal prestige should be replaced by the evaluation of contributions for what they bring, rather than for where they appear.
Here are some of my recent thoughts on this:
https://archeothoughts.wordpress.com/2017/06/28/the-academic-journal-is-obsolete/
https://archeothoughts.wordpress.com/2017/09/13/the-post-journal-academic-publishing-landscape/