It's a very simple game, but the gameplay works exactly as intended. The gameplay does get extremely stale quick, because there is not much to do besides holding left click and aiming at the targets. I'd suggest ramping up the difficulty or atleast having some extra features to the gameplay. This could be buffs, different types of enemies, etc etc.
Also, just because you are using GDevelop and I know the pain. I think the game you made would also benefit from some animations or any visuals upgrades, which from my experience is quite hard to do with GDevelop. If you feel comfortable enough, and with the game you have made, I think you could take the leap and expand to some better but perhaps harder software to make the games. Unity is cliche perhaps, but there are so many courses / tutorials online for it that it could be a great stepping stone!
Great work though!