If you're really don't care about the game, just spam easy mode.

Use all your free gacha and strengthen your team to as strong as you can get them, hopefully enough to 1shot the easy mode boss.
Auto choose skills and let the animation start. Scroll down and return to event homepage, the calculaitons are already done and you already won.
Start up another easy mode and repeat.
Collect rewards on the gift icon above the rescue button when you want and use crystals on the gacha.