From an idler perspective, other than the skill that gives you "energy" every second that you can upgrade, even when you're not in a match, there's no other idle components that I can see. A suggestion to the developer would be to consider an "idle" mode where the ball swings back and forth automatically but maybe less accurately/more slowly/less damage to still encourage active gameplay. I think this would still fit with the theme of the game because you can also just keep the game idle on the skill tree after unlocking those skills to accumulate points to upgrade, so there's already idle aspects in the game.
Edited to add: The developer is fantastic and very responsive to feedback. I mentioned Cloud save not being enabled and bam it was enabled shortly thereafter.