I've dabbled with trying to make a game over the last 5 years or so, and run into this problem every time. As a kid, I learned computer programming partially by making little Visual Basic programs and partially by making a couple dorky little 2D games.
At no point do I ever remember stepping back at my "work" and being frustrated to the point of giving up that whatever I was building didn't look like some professional thing I was trying to emulate.
I was mostly just happy that I could put something together, understand it and learn from it, and then see all the possibilities I could add to it and refine.
That feedback loop of "learn something new", "mess around with it", and then sort of spontaneously refine it and add new features, was super fun, and is what drove me to software engineering as a career.
For example, if I wanted to make a game, I would learn how to import a "sprite". I'd spend a little time drawing a crappy spaceship, and then be thrilled to see it on the screen, responding to key presses. Then, excitedly, I'd add an enemy. Then, "cool, I can have him shoot bullets and add to a counter every time I dodge one".
At no point did I say "my spaceship sucks, and I have no idea if I'm doing this scoring code right... I'm a loser and I'm done". I was having too much fun in the process for that.
But now? My attempts at making a game all start and stop with "I want to make an overhead shooter" and then I try to draw a pixel art spaceship and after a few hours of comparing what I do with the art in "real" games, get frustrated and give up. I want it to look and feel a certain way, and when I don't get that, I feel like the whole project is doomed to failure.
I don't feel this way with what I do professionally, which is primarily front and back end web and mobile app development. When I have to learn something new, I'm confident enough in my ability to learn and improve.
But my hobby stuff, and particularly artwork? Not happening, and I'm not sure how to get past this.
Some of this, I wonder, comes down to expectations of adults vs kids. As a kid, I never expected my stuff to be perfect or professional, and neither did anyone else.
Your picture of your kid's wall hit me. As a kid, I would proudly display my creations, and not care if someone nitpicked it. And of course, nobody did, because I was "just a kid".
But, honestly, if an adult proudly displayed a bunch of amateur artwork he/she drew, that would be really weird, right?
I'm capable of professional quality web development work, because it's what I've focused on for the last 6-8 years, but if someone were to see my amateur "pew pew" spaceship game, it would just be sad... if I haven't magically developed good skills here at this point of my life ("this point" being any point at which you are considered an adult), then I must just be bad at it, right?
I'm sure I can improve, but the combination of being embarrassed by everything I produce, along with a preoccupation with what everyone would think of it, and an impatience for being able to produce something good... it feels like a lot of barriers to get through.
And as a kid, I don't know what the "end goal" was, other than it was just fun to mess around. When I did release something online, I wasn't bothered by criticism and was happy at the praise, but mostly I just liked making the actual thing.
As an adult? Somehow the end goal feels like it's about the end result of releasing the thing, more so than the actual process of making it.
There's something about the lower expectations placed on a kid, and a lack of comparing everything I make to the gobs of talented people on Twitter or Pinterest, combined with a focus on the fun of just "messing around", that makes the whole process of getting better at something (and discovering new things along the way) much less frustrating.