Always make it obvious what a switch does, either directly by having its action affect something readily visible, or indirectly through a camera change, a message or some other mechanism to let them know right away.
Bad first levels are the worst, AC: Valhalla is a master class in story wankage. Your story better be fucking really exciting if you introduce like fifteen (15) characters I don't know and tell me I should be excited as the PC is meeting them.
Build your game around the player.
Doom 2 gives you plenty of seemingly overpowered weapons but balances gameplay by having you face waves of enemies instead of a handful of frustrating cheap enemies like Doom Eternal does.
Give the player a slight advantage such as making the player's hitbox extend a few pixels out further than the actual visibility of the attack like the chainwhip in 8/16bit castlevania games.