Feedback:
1. The gameplay is simple but effective. I would suggest you to make the player faster to add pace.
I understand the concept behind the game but just extuingishing fire is not enough. The fun factor is missing. Add something small and simple that adds a constraint. Maybe you need to pick up water to extuingish the fire, which involves pumping by clicking fast.
2. You pretty mush nailed the theme here. Your whole game is the theme.
3. Some of your art looks a little bit crappy which is an universal problem. Mine looks bad too. Maybe add real shaped things and not cubes. (I did the same mistake). Try out other things that don't involve pixel-art. Trust me it looks way better. Also adding light and post processing improves the visuals heavily.
4. The sound is mediocore. Im sure you did not have enough time. If you want to work further on your game add UI Sounds for player feedback, background sounds and randomized water sounds because it gets annoying after a while hearing the same sound.
Overall, 4.89/10
This rating is pretty good for a beginner (10/10 is like perfect game).
Don't take this feedback into your heart but into your brain.