
Don't be so hard on yourself. Kids always have big dreams and not much way to fulfil them.
When I was a kid, I dreamed of being a major soccer superstar, like Maradona. Then I became a teenager and dreamed of owning a car like Glottis's in
Grim Fandango:
(Hey, I said was a teenager. I didn't say I was smart.

The words 'teenager' and 'smart' don't often occur in the same sentence, unless the sentence is "Teenagers are seldom very smart").
I read
a lot of books (primarily sci-fi, fantasy, and crime fiction) in my teenage years and into my 20s. (Still do, I just diversified into mythology - which is basically fantasy, with all the supernatural elements and monsters - and hard science, which is sci-fi with its sleeves rolled up).
Then I hit 18 and dreamed of being an famous author, but I had no idea how to do it. So I started writing - at first it was QfG fanfic (which got better), then QfG song parodies (which got better), then experimented with loads of different genres and different types of poetry. Mostly humourous, but sometimes serious too.
I took writing more seriously about 3-4 years ago and joined a critique group. Learned a lot. I probably improved more in the last 3-4 years than I have in the first 20.

Still don't know how to get published, but at least I built up enough of a serious portfolio (and enough spare cash) to consider it. Maybe self-publishing? *shrug* Who knows.
So what was my point? I'm sure I had one.

Oh, yeah. When we're kids, we know what we want but not how to get there. We try a whole lot of different things - I can see
you did, and I know I certainly did (when I wanted to become an author - still do, though I've given up the 'famous' bit).
But wanting to do something creative doesn't make you an oaf.

The early experience helped you down the line, what with painting comic covers and D&D figurines and what-not.

Sure, that early sketch is nothing like what Sierra achieved, but they had so many more resources than you did. So good on you for trying!
