This is not a good platformer game. The design doesn't deliver a good experience especially removing the key for the sake of game progression isn't really a good punishment at all.
The game that has many open areas like this is more suitable for non-linear game. If the area is meant to be restricted, there should be some reward for stopping by or make it clear that it is restricted so that it won't display the misleading dialog.
The backtracking in this game isn't encouraging. There is nothing new to experiment with the stuff that the player has been before, and the player can't have fun from the use of player's ability because the use of ability can risk losing the game progressions and making more boring backtracking to recover progresses.
The choice of camera motion isn't a good idea too.
There are some good things in this game like graphics and sounds but with this game design the overall experience is ruined.