I think it's more of a will this update cripple our 20yr old in house developed app that is crucial for the business that either we don't know how to maintain or lost the source no longer working on the latest windows.

Previous employer, we were on WinXP and compiling a/ VS2003. Upgrade to Win7 mostly effectively crippled VS2003 for reasons I don't know. This necessitated porting our very large (100s of Millions of LOC in C++ to at least VS2008) set of in-house libraries. It should on paper be trivial, but it was a firm wide effort that spanned 18 months. Why? Because someone sent the CEO an xlsx that he couldn't open. This was circa 2007-2008. We were forced to upgrade OS and compiler for the new Office version, but it trickled into a firm wide rebuild of all C++ code. Wasnt pretty or fun.

It’s not supported and isn’t reliable enough to be cost effective. Microsoft barely supports what they claim to support, its bad advice to do this unless you have no options at all.

Being accountable for upgrading about 250k devices, we found that 3-5% of devices with questionable support status failed, as compared to near zero for supported devices. That 3-5% is unpredictable and expensive to address.

You also have to remember that Windows 10 isn’t a thing, it’s a lifestyle. Windows 10 1803 went EOL last week, and there are devices that worked with 1803 that won’t work with new builds.