Well, if you can not discern the mere craft of singing from its aesthetic result, you really do have bad taste.
And that without going into discerning Verdi or Puccini or Wagner from Rossini or Bellini or Donizetti, and they all from Mozart or Haendel or Bach, because what would become all those tenor voices and their precious singing when faced with the scores of the XVIIIth century musical tradition.
Apart from that, if I cared that much at all, leaving aside his sense of musicality, I would feel more outraged by the quality of Schipa's recording, than by Kraus' nasality and shortcomings in general: if I want to imagine how a score should sound, I have my own mind, I do not need a shabby recording of Schipa's, Kraus' or whoever else's singing voice.
I've just listened to his rendition of the 'Furtiva Lacrima', and it is a perfect further example of the point I commented before: excellent technique/s, little of music, barely any 'great' art... and canto drifting somewhere and nowhere among all that. You can admire Schipa as much as you want, and I will join you... but not beyond the territory in which he deserves recognition and praise.
All his great craft in the singing, which we all can admire in the terms presented in TIO, is destroyed by the decadent "musical" sensibility that grabbed two centuries of Western musical tradition to concoct that monstrosity commonly referred to as "Common Practice Period" which, as far as opera goes, understands that The Way to render anything composed between 1750 and 1925 should follow the Schipa's way, just like Toscanini was taken for the conducting standard... which is hardly The Way for any given period at all.
I concur with virtually everything being said in this channel about what is called "old" and "new" singers, and about theatrical wannabe modernism, but the author seems to forget that the sensibility that s/he seems to consider the "original", the "peak" of operatic achievement, was nothing but an old decadent "new" in relation to older traditions. It's not like there was a general standard from 1800, 1750 or 1850 on , that has been being destroyed and replaced only for the past thirty years or so.