No, disagree. I know plenty of people who are highly competent prifessionally, but deeply dysfunctional or plain horrible as people
Marten was a good-hearted, under-achieving doormat on day one and still appears to be one
I don't know what comic you're reading, Oilman, but it isn't the same one as me. I think that your essential negativity and your subconscious urge to disapprove of the strip is contaminating and warping your perception of the characters.
That must have been a freezer burn, because your delivery was
ice cold.
With all due seriousness, though, Marten is a chill, laid back dude. This makes him happy, and has directly benefited the stability of a lot of people around him, Dora, Hannelore and Faye have all benefited from Marten's non-judgemental, easy-going, wise-beyond-his-years counsel before.
Think of Hannelore hugging her father for the first time. Think of Dora deciding to finally be proactive about her relationship issues, and think of Faye realizing she had a drinking problem in the first place - after Marten jokingly called her a lush, of course. (Drunk Marten has, historically, made terrible decisions. But he does look
adorable in his worry-hat)
This is not the same as him being an underachieving doormat.
He does have the notable flaw that sometimes he finds it hard to assert his own desires. This is an
independent issue to his desire to help and support others, but the two do intermix. It can be hard to see where one aspect begins and one ends, but the simplest way to put it is: It begins where it helps his friends and ends when it hurts Marten. He's still trying to find that balance, and at times he has shown noticeable improvement. His dates with Claire, and how he's handling his new relationship, is
lightyears ahead of what strip 1 Professional Indie Ogler Marten would have been capable of. That's character development.
Pointedly, though, I'm pretty sure even Marten himself would disagree with you calling him an underachiever. Right now he pays his bills, he does his job well - much to his own surprise, at times - and he's happy. That last one's important.
Sure, the idea of being in this same place in twenty years
scares the crap out of him, but at the moment he has no idea what more he wants to work towards than 'be a guitarist in a band'. So what more is there for him to achieve? All he really seems to want out of life is what he has now... or being a rockstar capable of delivering orgasms with a power chord, either way.
It wouldn't even be unrealistic in my eyes for Marten's character arc to be that he comes to peace with the idea of living his life in this 'rut', surrounded by the friends that give his life meaning, and to realize
that is his achievement. That he's happy and he makes the people around him strive to be better. Not all success is measured with dollars and decimal points.[1]
In fact, he's even taking steps towards that end, as much as Claire has rocked his world with armour-piercing questions.
You have to ignore
literally everything about what makes Marten who he is to
only think of him as an underachieving doormat.
[1] I have no idea what he'd do with more money anyway. Buy more guitars, probably.
EDIT: Addendum - Heraclitus once said that the Oxen is happy when it finds a patch of bitter vetch to eat, but that is not happiness we should aspire to.
Dude was famously miserable. Fuck that noise. If Marten's bitter vetch just so happens to be the mutual love and support of those around him, let the dude be happy doing what he does.