The optionality of being cloud agnostic comes with a huge cost, both because of all the pieces you have to build+operate and because of the functionality you have to exclude from your systems.
I am sure there are scales where you either have such a large engineering budget that you can ignore these costs or where decreasing your cloud spend is the only way to scale your business. But for the average company, I can't see how spending so much on infrastructure (and future optionality) pays off, especially when you could spend on product or marketing or anything else that has a more direct impact on your success.