The first-up online dictionary gives two distinct meanings for the adjective "worthy," viz:

1. having or showing the qualities that deserve the specified action or regard.
"these issues are worthy of further consideration"

2. characterised by good intent but lacking in humour or imagination.
"worthy but tedious advice"

That second meaning is common in the UK, but, oddly, when I looked it up in Merriam-Webster online it wasn't there. It sort of means competent enough but just dull and uninspiring. The point is, to extend that into a noun you would say "worthiness." Which is what I meant in that earlier post. I'd be interested to know if the word "worthy" is ever used in that sense your end.

It might be worth adding (see what I did there?) that we also have a noun "worthy," as in "The public meeting was attended by the town's ceremonial bigwigs and quite a few other local worthies."