Why do you think the unit economics of Carvana have to be worse than a traditional dealer? Maybe they have to do more shipping of vehicles around, but they are less reliant on storefronts/sales staff. It seems likely to me that they overspent on marketing/gimmicks/badly timed top-of-market inventory, but that doesn’t mean that the business model fundamentally can’t work.
A higher cost higher quality service can succeed, but that's not the Carvana business model. The Carvana "business model" was "sell as many cars as possible and work out the economics later" and it's now "try to lose less money by any means necessary" (including by sacrificing quality of service).
I am not theorising about their costs, rather, I am referencing their own financials. Per their financials, they must achieve >$4,500 in gross profit per car sold in order to break even on a sale because the cost of providing their service is around $4,500 per car. As far as I know, they have never achieved this and they have only come close during periods where the second hand car market was at its most ridiculous supply-chain induced peaks.
You could start an online second hand car dealership today, with the same online purchasing that Carvana offer, and a better quality of service, and build a great business with great unit economics... if that was your strategy from the first day. Many such companies exist! There are lots of upmarket car dealerships that'll give you excellent service -- and it'll cost you less than $5k over market.
Carvana can't just undo a decade of bad mistakes, they can't just switch from "losing money" to "making money" because every foundational decision about the business was made in the context of "who cares about money, we want growth". You should not think of a company as an implementation of a business model, a company is so much more. Carvana has something like 20,000 employees: at that scale, radical change is basically impossible.
