Saying “she had potential” is usually used in this context, he realized his mistake after the fact.

https://www.urbandictionary.com/define.php?term=She%20got%20potential

Although usually referring to underage girls, in this case people were roasting him in the comments because of the usual use case.

I second this. There is also a near infinite number of maps with the steam workshop, some of them are really good.

Web based, try Pixlr. Very similar