I'm curious why you were downvoted. I have found animations do slow down my phone. When I press the home button, as the apps fly in, I can't scroll left/right until the animation is done playing. I have reduce animations turned on (accessibility settings, I think) as it makes my phone feel a lot faster.

Also, I remember the calculator app being unreliable due to animations: https://www.macrumors.com/2017/10/24/ios-11-calculator-anima...

Is this not a legitimate problem?