> If you run MacOS on non-Apple hardware it isn't officially supported at all
By "officially supported", what I mean is that Apple supports VMWare in developing drivers for ESXi, so neither new versions of ESXi, nor macOS updates, will suddenly break macOS ESXi guests. You can put the same expectations on the stability of the ESXi hypervisor in running Apple software as you can on Apple hardware in running Apple software. (This contrasts with the Hackintosh driver ecosystem, where every time macOS updates you have to figure your compatibility out all over again.)
Now, the other half of that—the stability of your hardware in running ESXi, etc.—is up to you. Obviously, you can't take your Dell into an Apple Store and expect support.
VMWare sort of does support you, though, insofar as it's the free-tier support (you can get better if you pay for VSphere), and insofar as whatever problem you're facing is a problem with ESXi—or a problem in your hardware's ESXi compatibility—instead of a problem in how ESXi handles macOS guests. But, as I said above, the latter is Apple's problem to worry about; such bugs get fixed, to support the people who are virtualizing macOS on Apple hardware.
> the fact that ESXi won't do it unless modified
Not actually true! ESXi won't create a macOS guest without hacks. It's perfectly happy, however, to import a macOS VM created using VMWare Fusion. There's even a quick menu-action to upload VMs directly from Fusion into ESXi.
> Except the license agreements (both Apple and VMWare)
A license agreement doesn't stop you from doing anything. It doesn't have hands to restrain you from typing the commands that will install macOS. You stop yourself, because of a license agreement. Or you don't. Up to you, really. It's not like either Apple or VMWare is going to stop selling you their products, let alone sue you, for what you do with their software on your own computer.
(Now, if you're an employee of a company, then the licence agreement might indeed have "hands" to stop you with: the hands of the lawyers of the company, enforcing the company's agreement with VMware/Apple. This is why https://macminicolo.net/ exists, instead of just being an ESXi farm.)