Why is it a cautionary tale for first movers? From all the popular discourse about PUBG, it seems as though while the game idea and core game play is great, it'

Why is it a cautionary tale for first movers? From all the popular discourse about PUBG, it seems as though while the game idea and core game play is great, it's terrible in execution. They had ample opportunity to leverage their lead to address their problems, but didn't. This allowed Epic to copy all the desired components, and address the issues as yearned for by the gaming community. I'd say this is more a cautionary tale to people who stumble upon a success. Just because you got there first, doesn't mean you can stop shoveling.