It's a fair question Dave, but relatively easy to answer.
It is widely accepted that this group of players is the most talented group at Everton's disposal since the mid 1980's. Martinez of course must take credit for this, I acknowledge that totally.
Secondly this season we have seen Manchester City, United, Chelsea and Arsenal (perhaps to a lesser amount) underperformance and allow Leicester, Spurs and West Ham to challenge at levels beyond what you might expect their 'natural' position might be. The common factor amongst these three clubs is that they each have a management team which through tactical ability, and the ability to prepare and instil belief in their teams have created teams performing beyond their expected abilities.
However at Everton the absolute reverse has happened. Far from being greater than the sum of our parts we've become less than the sum of our parts. Tactically we are moribund and devoid of an ability to change the course of games. Mentally we are completely shot. We have no expectation of success on the pitch and we have become a "soft touch" - not a characteristic you'd ever expect to hear from Everton.
All of the above plus what will become rapidly very changed expectations of how we define success means Martinez' position is untenable. For all his good intent, and I think he's a deeply honourable man, he does not possess the necessary skills and therefore by the end of the season I believe he and his team will be released - with just cause.