If you pluck that out it completely freezes 50%+ of their operations, people really don't get how much stuff in modern companies is reliant on MS stuff (and thus why they are one of the richest companies on the globe)
Moving away from that would be a massive change management undertaking, but it's not the "Office" part which is our primary challenge. To be fair, I'm not sure we could actually survive the change management required to leave the Office and Windows part, as it would be completely unfamiliar territory for like 95% of our employees, but the collective we at least think that we can. We have quite a lot of Business Central 365 instances, the realistic alternative to those would be Excel (but not Excel). SharePoint is also a semi-massive part of our business as it's basically our "Document Warehouse".
I guess maybe I'm using the 365 term wrong?