If you absolutely need to scale something vertically, IBM Z is the final stop on the line.
X86 is great at hosting an entire farm of applications. You would never want to install salesforce or gitlab on a mainframe. That would completely defeat its purpose. If you've never encountered an appropriate workload, IBM might never make intuitive sense.
Also, the roadmap:
https://newsroom.ibm.com/2026-08-24-ibm-unveils-next-generat...
Lots of work went into integration and it never went live.
For one thing, amongst many, IBM mainframes process 70% of global transactions on a value basis