I convert about 17 Debian machines with Debian 8 with little or no problem.
(I understand that you need Debian 9 but that is my experience).
I'm think your problem is about the virtual hardware versión of
destination in your ESX.
I have all my machines with Virtual Hardware version: 11
Read this links, may be help you:
[0] What other requirements and considerations are there for virtual
machines with EFI firmware?
[0] https://communities.vmware.com/docs/DOC-28494
[1] https://communities.vmware.com/thread/519642
Here [2] say that
"(...) EFI firmware is supported from hardware version 11 and above. (...)"
[2] https://communities.vmware.com/thread/584625
[3] https://akmyint.wordpress.com/2012/09/30/my-p2v-notes-stand-alone-servers-or-non-clustered/
I'm a Spanish speaker, sorry for my bad English.