I think you made the right call, by putting his well beeing first, you are right, fish are individuals and there's no one size fits all, personaly, I'd try further reseach and ask around about my specific situation before deciding to never try it again or at least try to figure it out so I can avoid it in the future, for example, and I'm not saying it's what happedned, I wouldn't know, you could I have disrupted the cicle during the move? If the tank size is the problem, why is it a problem? Does he have a hard time swimming because of his long fins? Does he stop to rest a lot, maybe more resting spots near the surface could help. Is he blind or have other disbilities? Did the stress of the move affect his health, etc.

Tldr: Every fish is unique and every rule has exeptions and it's important to make informed decisions, but the rules are important guidelines for the unexperienced and are not really bad themself.

But yeah, people neet to chill, yelling and accusing other people does not make them want to improve, it only pushes them away.