You can be both too acidic or too alkaline, and both can lead to sickness and death. It's all about balance. and eating healthy helps your body maintain that balance. This article explains it well.
The Myth of Alkalizing Your Body - Center for Nutrition Studies
Should you alkalize your body or eat more alkaline foods for better health? What does ‘alkalizing your body’ even mean?
https://nutritionstudies.org/the-myth-of-alkalizing-your-body/