I’m not sure how you could suggest starbucks and mcdonalds outcompete based on product quality or ambiance. Have you been to a random mom&pop coffee or burger spot recently?

Chairs aren’t magic, we know roughly what’s good or not. You don’t need a PhD to choose a good chair. A mom and pop could just copy the chair too.

The chains outcompete on marketing, leverage with vendors, etc.

They put a huge amount of effort into baseline quality because it’s incredibly hard to pull off across 1000s of stores staffed by people who don’t have any incentive to care.

You gave me an idea I've not thought about before: whether large corporations view peripheral companies (like Uber Eats, Door Dash, etc.) as friends or enemies...

While mostly correct it is missing that not all customers in all stores want the same.

Customers in store A might have wildly different preferences to customers in store B. Starbucks can't account for that - small stores can.