- Decline in quality of food: As far as I know, pan pizza in the 90s at Pizza Hut (that the article talks about) had the dough made in house; modern versions have reheated frozen dough. I feel like this is an important distinction. If I'm just reheating frozen pizza, I can do that at home.
- Decline in quality of service: The article mentions this in passing (server knowing the order of a frequent customer) but doesn't go any deeper. In my experience, a lot of the servers (not just at chains, but everywhere) these days are younger people who seem pretty indifferent to the customer experience. Certainly I don't think that any servers at a Pizza Hut will remember someone's order in 2025.
The factors I mention above are hard to measure, especially over time. But I do feel like they have contributed to the decline of chains to some degree as well as things like orders to go, did delivery apps, etc.