I agree with the OP.
Now then, on to the juicy bits.
From the consumers perspective, just what does a genre mean to you? Imagine you have no idea what a “Massively Multiplayer Online” game is. Using your best layman judgment, what does it tell you as a description?
Massively -Okay, so… we’re talking large scale…-ish?
Massively Multiplayer - Ah… right. So I assume the game is massively based or heavily dependent on multiplayer? …Go on.
Online - Ok, cool. So I just plug in my 56k connection and I’m good to go. No more lan parties, YES!
What else does it say? Does it say anything about there by chance being large worlds? Small arenas rather? Hell, maybe it’s a card game playing 1v1 and I can play all those people online …eventually!
Clearly, “MMO” is a very ambiguous subject, rather a fancy term for “Multiplayer Game” held to a higher standard… sorta. Now then, the above questions can be answered hopefully by reviewing your title cover. All a genre means to do is categorize where on the shelf it belongs by describing your game in as few words as possible. “MMO” or any of its counterparts don’t do that efficiently enough.
I personally believe the MMO genre should be retitled to something more appropriately fitting, but not restricted by the constraints of this argument (suggested mechanics, etc). The idea being simple enough, if you have a multiplayer FPS game, It’d be an OFPS - Online first person shooter. Likewise, an MMORPG would simply become an ORPG and so forth. Very standardized and uniform.