Fair enough on limited resources. But this is a preference that people that want a Mythic Martial don't share obviously, and for this crowd I would think getting a Mythic Martial is a high priority. Unless there was a real study done (not that sad D&D Next stuff) we don't really know how many folks fit into each category. My hypothesis is that there a bunch of folks that fit into the "really want the option and would jump to play it" and the "may not always play it but think the system would be better off with it as an option amoung others including the current martials".
In terms of core themes of D&D -- the disconnect for me comes from the fluff that martials often get that seems to describe them as equals of Wizards at higher levels without the mechanical backup. I tend to gloss over the 5e fluff so not sure if it's as prominent in this edition but it was in the past.
Not saying you specifically, but in terms of not liking others fun, Mythic Martial supporters don't mind the current Fighter existing while some current Fighter supporters really don't want the Mythic Martial. Resource contraints aside, this comes across as gatekeeping. Also many people that don't want Mythic Martials seem very, very vocal on what the Mythic Martial should look like despite the fact they they don't understand why it's needed, don't want it in the game, and will never play it. I think as long as the Mythic Martial is no more powerful, versatile, and narrative controlling as the Wizard, then the people that actually want to play the Mythic Martial should be catered to and not the people that don't understand why it's needed, don't want it in the game, and will never play it.
Ah, zero-sum everything is magic, then.
