> Let’s stay on topic and actually ask the author why such a complex setup instead of assuming you know and speaking off the cuff with criticism

I'd go a step further and say the question of why the author may or may not be overengineering their own app is besides the point.

I'm not saying asking out of curiosity would be a problem, but it shouldn't be construed as at all relevant to the very valid points OP is making regarding Vercel's service