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I have to disagree with MJO, both on the point that Weinen, Klagen, Sorgen, Zagen is out of place or 'degenerarate', and that it is a peculiarly Latin trait, as no one who has spent time at Colmar or Carlsruhe will easily agree. But for some paroxysms of its history there might be plentiful examples to point to in England as well. Come to think of it, is there anything in Guerrero approaching the gruesomeness of Cornysh's Woefully arrayed? I find myself in a little sympathy with the Youtube commenter who complains of "an unwavering, unvarying, wearying mezzo-piano and they have sacrificed interpretation for a homogeneous, blended uniformity. "

Tasteful decoration? Sure.

I think, though--after having surveyed fifty years of the output of the "historically informed performance" crowd--that we need to stop idolizing the exact conditions and practices of the past when we have the capability to do so much more with the level of training and knowledge we have nowadays. Were singers typically accompanied back then for some pressing artistic need, or merely to keep them in tune? The biggest example of this in my experience is the oboe part in Handel's Messiah, which ruins the texture of four equal polyphonic voices to nonsensically double the sopranos for intonation reasons. Such a contrivance is obviously practical, rather than musical, in construction. If your singers can keep in tune perfectly well on their own, I'd much rather hear their mathematically perfect intervals than the necessarily imperfect compromise of an organ's equal temperament.

I similarly don't buy that the particular style that people like Bartolucci champion is anything other than antiquated. His performances of much of the Renaissance repertoire may be as lusty as they were in the sixteenth and seventeenth centuries, but they make it impossible to focus on the actual music itself because their downright self-indulgent method of performance obscures any sense of tonal relationship or linear interplay in the polyphony. Such an approach can only be described as hopelessly dogmatic.

In fact, I would argue that the performers who are impossibly out of touch with the true meaning of the music they play, and unfortunately monotonous, are the same ones who are so slavish to "exact performance practice", trying to follow every scholar's recommendation and every line in a period treatise while sheepishly pushing out the notes as though the whole score is under museum glass--and the ones who are the most emotionally expressive are those who, in the moment, could not care less what some bookworm thinks and merely approach the music with sheer intensity and honest feeling for all the emotions and interplay of basic elements contained within the score.

There is no such thing as a "recipe" to a perfect performance--something that I fear we have become obsessed with ever since the recording age kicked off. If you approach the music honestly and with the deep feeling it deserves, and take any additional period knowledge of the composer as relative to the score and to that feeling itself, and if you can inspire your fellow musicians to do the same as well, then you will arrive at a musicianship which nobody's pedantic criticisms will be able to assail. But if you are either too self-indulgent or uncaring (as I suspect many of the "sloppy" musicians of the past often were), or too devoted to exactly reproducing what some scholar thinks the music sounds like (as I suspect far too many musicians of our generation are), you cannot hope to become a proper artist.

After all, the Victoria "O Magnum" sounds exactly the same, whether it's sung by the Cambridge Singers, The Sixteen, Tallis Scholars, King's, New College, Christ Church, Ely, or Westminster (either one).

This strikes me as quite an exaggeration. Here are a few YouTube performances by most of these groups, as well as some others. I find quite a variation in performance. The performances which exceed 4 minutes by very much are, to my taste, too slow. The range 3m30s-4m00s seems about right to me, at least in most cases. The old saw that in most Renaissance pieces the tactus should be approximately 60bpm goes out the window with all of the performances (at that tempo, the work would come in well at about 2 and a half minutes!).

Cambridge Singers (4m17s): https://youtu.be/9xPh-fXYAc4
Cambridge Singers (4m01s): https://youtu.be/udVeFKw095E
The Sixteen (3m28s): https://youtu.be/eDAQtZz1yf4
Voces8 (4m01s): https://youtu.be/1sKEF1xilOY
Robert Shaw Festival Singers (4m14s): https://youtu.be/zSPaJLXfd-w
Robert Shaw Chorale (3m31s): https://youtu.be/7wWcnCb6Yjg
King's College, Cambridge (3m24s): https://youtu.be/wro_AYqnKpc
Carols from King's, 2016 (3m17s): https://youtu.be/uJNeuF_eiyU
Chanticleer (old, 3m47s): https://youtu.be/hg1l65xiGkY
Chanticleer (newer, 4m00s): https://youtu.be/CRGWPuMHCSw
Voices of Ascension (3m38): https://youtu.be/fxwf_YlUDPg
St John Cantius Choir of Saint Cecilia (3m08s): https://youtu.be/VgSJ1ywG4ME
New College Oxford (3m52s): https://youtu.be/ZcaoAwfaTg4
New York Polyphony (3m25s): https://youtu.be/JGXERrZKOC0

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[A]dopting the liturgy of the 1st Century to incite the piety of the 1st century...and we see where that devilment led.

Save that we don't have the liturgy of the 1st century, we have the liturgy of the mid-20th century, masquerading as the liturgy of the 1st century.

To adopt the performance practice of the 16th century (or the repertoire of the 16th c.!) in hopes of inciting the piety of the 16th century

No, not hoping for that at all.

... as a sample of the application of some standard ornaments

Well, I'm sorry to add something negative about this but: putting the same ornament in all voices at the same time strikes me as some sort of artificial overkill or ... to put it differently ... just out of place.