First, I want to be absolutely clear: this is one of those situations where a guy [me] who has never worked in a particular business [pizza] mouths off about how that business is CLEARLY organised wrong and should be completely reformed. Here be dragons, reader beware, etc etc etc.
As a consumer, it seems clear to me that the biggest determinant of how tasty a pizza-by-the-slice kind of pizza-slice will be is how recently it came out the oven. Re-heating the slice individually just doesn't work the same, it gets your slice hot(ish) but it doesn't get your slice fresh. I would rather have [any topping I can eat] on a fresh slice than [my favourite topping] on a stale slice.
As a result, I'm irrationally convinced that almost-all pizza places are Doing It Wrong. Instead of making 10 different pies and laying them all out to get stale while they wait for a pieful of slices to get ordered, they should make one pie at a time so that every customer gets a slice that's piping hot and [whatever the equivalent of "piping fresh" is].
An inordinate number of people seem to dream of starting a restaurant where there's only two choices on the menu each day: a Classic and an Interesting choice. If it's a pizza place, you'd basically choose between plain cheese and Today's Special, which would be something original and creative. Many people I know claim they want a place like this, that they hate making choices in restaurants and this would make it fun and easy to order, and ~no restaurants provide it, which makes me believe that people don't actually want it but just imagine they would.
So I won't make that rookie mistake here: people clearly want toppings on their pizza, and a choice of toppings at that. My contention is that there's a missing insight: the toppings don't have to be cooked directly onto the pizza. It seems reasonable to me that you could pre-cook a bunch of toppings and then add them to a (deliciously fresh!) cheese pizza, the way that assembly-line burrito places add your pre-cooked onions and peppers and whatever to a burrito. You could even pop the slice back in the oven once the toppings are added, giving them a bit of a brown and embedding them more into the cheese.
Will this be as good as having toppings cooked into the pizza directly? I'm sure it won't, but that's not the question. We live in a fallen world of tradeoffs and compromises, and the relevant question is rather: which tastes better, a fresh slice of pizza with toppings added seperately or a staler slice of pizza that had the toppings cooked into it? It seems implausible to me that the latter would win this fight, especially since the very best pizza topping (black olives) doesn't need to be cooked at all.
High-end sit-down pizza restaurants would of course continue to cook specific pies to order with the toppings there from the start, and I applaud them. But since a significant share of (American) pizza is consumed by the slice, and the implications for human flourishing of improving low-end slice-pizza production by even 10% are astronomical. If you've actually worked in the pizza business, I would love you to tell me why this simple dream is beyond our collective grasp.