David, I agree with you, that learning to do things in camera is essential but I think you need to climb down from your high horse. The OP asked for any tips that would help him improve
That's exactly what I did: Gave him tips to help him improve. You told him how to improve THAT image. I'm telling him how to IMPROVE. That's not a high horse.. that's common sense and the correct way to teach photography. The guy probably, given the choice, would rather be a better photographer instead of knowing how to botch up his mistakes.
To quote the old proverb... give a man a fish, and he'll eat for a day... teach him how to fish etc etc....
If he's got no interest in becoming a better photographer, then fine... I stand corrected, and admit the advice wasn't necessary, but assuming he does want to be a better photographer (a reasonable assumption given where we are) then your advice will do precisely nothing to achieve that goal, so what was the point of it? This is someone struggling with understanding exposure and lighting, the two fundamental aspects of photography that more than anything, determine whether an image is technically good or not. Post processing does nothing to address that. Nothing.
Post processing is a fact of life, as it always was, in the film days. We may have more latitude in the digital age, but it would be incorrect, not to highlight post processing as a tool.
As a means to embellish, or improve an already solid image, yes. I use it al the time.. extensively... probably a great deal more than you do. Not as a means of avoiding skilfully producing imagery in the first place though. The OP's image is not the result of an unavoidable mistake (which I admit is a valid use for it). It's the result of not knowing some stuff that no amount of post processing will teach him. Fact.
I don't know why I bother though.... The same people I see doing this.... Person posts an image displaying technical problems caused by poor camera skills or lack of knowledge and asks for tips to improve, and they "correct" his image for him and repost it as a means of looking knowledgeable and cool, and say "Just needs a bit of PP". That's not what we should be teaching, sorry... it's just not, and if saying so makes me seem like I'm on a high horse in your opinion.... then I genuinely don't give a damn because you need to know you're teaching the wrong things, and not helping anyone improve as a photographer, and that.. is a fact. This isn't about YOU, or Gramps.. or ME or anyone else; It's about the OP. He needs to learn the basics of photography if he's to improve
as a photographer.
Teach the post stuff later..... once he knows what he's doing. You wouldn't teach someone how to repair their car when they crash it... you'd teach them how to drive first, so they don't crash it.
After all that... after you've corrected his exposure for him.... he's still got to understand why it's his lighting that's really letting the image down. You really are muddying the waters, and you just don't realise it. Technical camera and lighting skills first.... PP later. No amount of PP will help with his lighting anyway. Fact.
But hey.. WTF do I know. Carry on.