It's May 6, 2022. You're launching your startup next month. Are you going to host on-prem? What, with server equipment backlogs now 4-6 months, and that's if you're a large enterprise customer? Network equipment backlogs are now in the 8-12 month range. Not to mention the cost of needing conditioned power, cooling, staff, space, etc. You're going to utilize the cloud. It'd be insane to do otherwise.

You do raise a fair point - what about the applications that are more economical to host on-prem? In my own portfolio I estimate 20% or so of my applications make more sense to host on-prem. What to do about those?

The most practical option is to mandate every application you build in the cloud have a plan for how to run on-prem. Note those that would be very difficult to run on-prem - those are your key cloud dependencies. For example, in my own portfolio I have a couple of applications depending on Lex and therefore would be very difficult to host on-prem.

Pay special attention to your so-called "crown jewels" - your apps that distinguish you from your competitors. If those were dependent on a key technology such as Lex and would be difficult to migrate on-prem then you need to identify other cloud providers you could migrate to. In this particular example I know Microsoft's and Google's clouds both offer similar services.

If you design and build your applications with no thought of the future then you're already in a bad position.