I don't see the appeal to it at all. The structure building aspect has no appeal to me in a battle royale first person shooter. I don't like the cartoony nature of it, and the mechanics and shooting look way too dumb down and tailored for casual players. Maybe that last part is why it's popular though. It just plain doesn't seem like a good game.
Also while PUBG definitely has it's problems, the developer who makes it can be douchebags, they don't know how to optimize or patch the game well, they don't listen to their players, it's obvious they weren't ready for primetime and the unexpected success they had, and they have pretty much totally squandered the whole catching lightning in the bottle with the battle royale concept and let themselves be overtaken by Fortnite I have to grudgingly admit it's both better than Fortnite and Fortnite just very shamelessly ripped them off.
The battle royale FPS concept might appeal to me more, but first some other studio that has a lot more resources and can do it right will have to make a game without the flaws of the other two have.