In my own testing from Nov 2017, I got GUI Emacs to run.. it was slow, but it ran.
Vanilla GUI Emacs runs a non-trivial amount of eLisp code, so at least then with the version of Emacs I used (24.4.50) the compatibility situation could not have been dire than what the OP reported.
Also, you have to bear in mind that Guile Emacs was the work of one single (very talented) person over a single summer.
If there was actually a team of people working on it, I expect a lot more progress towards compatibility could be made.
Here is a list of outstanding items that still need to be worked on Guile Emacs:
That is because op didn't run it in Emacs. Guile-emacs uses the same Emacs c functions that Emacs elisp does, and running the Emacs tests against guiles elisp-without Emacs is like taking away a huge part of the standard functionality and expecting things to run.
The points it makes about speed are not wrong, but that the author fails to understand even the most basic relations between Guile-emacs and guile-elisp makes it hard for me to take it seriously.
Guile Emacs is not at all compatible with Emacs Lisp, it only implements a tiny subset of Emacs Lisp.
It's right there in OP's article.
So the only thing it has going for it is being .. Lispy. Not enough.