One reason serverless isn't the solution for most applications is that you're basically making yourself entirely dependent on the API of one specific cloud host. If Lambda decides to double its price, there's nothing you can do about it but pay. If you need to store your data in a specific place (for example, in Russia, because all Russian PII must be stored in Russian borders), then you're out of luck. And best of luck to you if you're about to catch a big customer but they demand your application to run on their premises.

There's also the long-time guarantee; if you write an application that runs on Ubuntu Server or Windows Server now, you can bet your ass that it will still run, unchanged, for another 10 years. The only maintenance you need to do is to fix your own bugs and maybe help out with some database stuff. If you deploy a Lambda app now, you have nothing to guarantee compatibility for such a long time other than "Amazon probably won't change their API, I think".