If you are a very big SaaS company that is not Google or Apple, you are probably serving hundreds of thousands, maybe millions of unique users. AWS may be convenient, but you don't /need/ it, you can build an infrastructure that will handle such workload with any of the big european providers.

You'll just lose in comfort what you'll gain in data sovereignty and infrastructure costs.

I worked for a 7M€ MRR company that had maybe a million of users who used the software every day. The thing ran on a dozen of OVH servers, including multi-site redundancy.