The Processor must offer VT-x virtualization (and possibly further virualization technologies). This may not be available with older processors. IMHO Xeons do lack this feature, while Core i7 processors should definitely have it.
But even when the processor supports VT-x, it may be blocked by firmware.
Apple has an article “If VT-x virtualization technology is locked or disabled on your Mac” at https://support.apple.com/en-us/HT203296 that lists EFI updates to fix this problem.