From what I've seen, Oracle Cloud usage is mostly to lift-and-shift legacy Oracle software packages off-prem and things that need low-latency access to them.
It's more Oracle software as SaaS, some basic IaaS (more like a hosting provider than a cloud) and hosted Oracle databases (which are just Oracle running Exadata for you).
So it's big companies struggling to get off old Oracle (and acquisitions like PeopleSoft) stuff and it's gross.
I don't know of anyone using it as "their cloud", but more of another thing to mix in with AWS/Azure/GCP to get rid of on-prem or colo facilities. It's more like IBM Cloud: A way to hang on to customers, sell services (human services like consulting and support), and keep milking those old products for big companies.
I should mention that you can't run Oracle RAC on any "real" public cloud, because it doesn't play nice with SDNs and needs shared block storage. People have done it with hacks (like VPN tunnels between hosts), but it's not performant and well, an unmaintainable hack. I've seen things like read-only single instance replicas of on-prem DBs, but uhhh.
A stand-alone Oracle server isn't a reliable solution because patching = outage. So Oracle providing managed Exadata is a win for some (again, usually big) businesses.
Oracle got a lot of companies hooked on proprietary DB features and rewriting can be painful or require spinning up a dev team for something in "maintenance mode". Even Amazon just fully got off Oracle a couple years go IIRC.
Just as a counterpoint, regarding your IBM Cloud snub, my small company has been doing our cloud needs with IBM for the past 5ish years, with great pricing, stability and support. The portfolio of non-ibm-specific services is huge.
It's more Oracle software as SaaS, some basic IaaS (more like a hosting provider than a cloud) and hosted Oracle databases (which are just Oracle running Exadata for you).
So it's big companies struggling to get off old Oracle (and acquisitions like PeopleSoft) stuff and it's gross.
I don't know of anyone using it as "their cloud", but more of another thing to mix in with AWS/Azure/GCP to get rid of on-prem or colo facilities. It's more like IBM Cloud: A way to hang on to customers, sell services (human services like consulting and support), and keep milking those old products for big companies.