I was maybe a bit too vague on the fun aspect, which is, above all the rest, very subjective and it really depends on target audience expectation.
This is something I’m still learning myself, who is the target player for our games? For a pacman clone/reinterpretation I expected a faster and challenging game. But, once again, this comes from an avid arcade/action player.
About the battery, most of the times I stumbled upon a battery with full stamina, so unless you can pick them up and use it when out of stamina, I don’t think they add a lot to the gameplay.
About “just (…) gathering the flowers”, I don’t think it makes a complete game loop by itself, without the added challenge of escaping ghosts (which is what made the OG Pac-Man interesting).
About, “using the mechanics correctly”, if it’s not explained to me as a player (which is always dumber than the game developer) I can’t use it correctly ;)
Anyway, keep at it! A 3d game is not a small achievement! Well done!