I think the use of the term friendzone that's problematic is the PUA who sees a friendzone as a mutable object -- a literal place, that he just needs to penetrate through, like it's his little challenge that will test his manhood and worth. The garden variety guy who just got rejected and is like "aw, damn, I'm friendzoned!" doesn't meant it that way, and doesn't need Tumblr jumping on him, kicking him when he's down, assuming that he meant that in the absolute worst way that is possible to mean it. How does that help anything or anyone? Because guess what, the vast majority of guys are NOT PUAs and are in fact trying to be sensitive as they go about this whole dating thing.
P.S. Do yourself a favor and read less "Fedoras of OK Cupid" and "Nice Guys of OK Cupid." They are obviously making you believe those are random and representative samples if you really view the use of this word as a "problem" (your word).