"it seems silly that you can just go around the corner and suddenly you're hidden. They know you're there"

This was rebutted with "they know I'm somewhere over there, but not exactly where or when I'm going to pop out. I'm a 7th level rogue, I'm sure I have tricks you and I can't even think of".

Sometimes people get like selectively simulationist. They'll ignore most of the game's gamey bits (inventory management, hit points and recovery, magic) but some things throw them off. Usually things that are closer to lived reality. For example, someone having no problem with a wizard hypnotizing an entire room, but balking at a fighter climbing a tall fence.

There was also: "It seems like a lot of damage..."

"I'm pretty sure rogue is balanced around doing sneak attack almost every round. The fighter gets multiple attacks, but I don't. Almost every other class gets a resource to burn like spell points or ki points or superiority dice. I have nothing. All I do is sneak attack. Without it, I'm a particularly accurate peasant that can run away real good. And I still miss about a quarter of the time, which means my whole turn accomplishes nothing"

I wonder if the DMG or something published expected damage per round or per encounter somewhere.