Now, database replication, not having to waste time to run/maintain clusters (be it Kubernetes or Elastic stack or something else), that I believe is well worth the money to offload to someone else, but even there you can get a much cheaper deal with someone that's not one of the three big cloud providers. I will also concede that Firebase is genuinely nicer to work with than its alternatives (Supabase very much included).
I run a PowerShell script once a day at noon, and I have no idea what kind of server it's running on, where in the world that server is, how much memory it has, or any other details. I get about a CPU, a dozen MB of memory, and a tiny amount of network capacity for about 5 seconds.
This is a very different experience from "We will rent you a VPS by the month".
Clouds give you software-definable load balancers, networking, clustering, integrated systemwide security, and a boatload of managed services like message queues, databases, AI training and inference, etc. etc.
No-one sane implements all that using a collection of VPSes, because of a simple principle of business: it's more profitable to focus investment on your core competencies, and for almost all companies, managing a non-trivial computing infrastructure is decidedly not a core competency.