I do not disagree with anything you have posted ROWUK however for myself I hear great beauty in ancient instruments.
You mentioned the Cornetto and I have some experience and knowledge of these instruments so I feel I can speak on the topic.
For example a Cornetto played in its traditional setting in a church or a cathedral with an organ accompaniment is a beautiful thing.
There is a seductive sweetness and beauty in the tone of a well played Cornetto that I have never heard in any other instrument.
Of course modern instruments are wonderful and highly developed and sit well together in an ensemble and sound wonderful in a modern setting and playing from a modern score.
But my point was and is that the ephemeral gentle and sweet alluring tone of the ancient instrument appears to have been lost in the shuffle over the last 300 years.
Is the modern instrument better, yes it is, it is in tune with itself it is consistent in tone across its range it is relatively easy to play well in all registers and its wide dynamics are helpful in developing expression.
The old instruments have issues with inconsistency of tone difficulties in controlling pitches and dynamics and sometimes it feels they fight us. But that was not really the point these inconsistencies are part of the charm of the instrument.
For all their faults the music made on these instruments is compelling and addictive. I have played recordings of ancient instruments to various members of the public and without exception they have declared the ancient instruments to have great beauty of tone.
Today for example I played a cornetto recording to a lady of advanced years and she told me that her hairs stood up on end when she heard the instrument and it touched her in her soul.
I also played a recording to a young man of around 17 or 18 and he declared it to be surprisingly beautiful.
Of course that can happen with modern instruments but it happens repeatedly and often with the ancient instruments.
I firmly believe that we have lost something precious by leaving these instruments in their cases and exclusively playing on modern instruments.
You are right ROWUK we have gained a great deal in the development of our modern instruments but we have also lost something.
It is however easily fixable by our simply obtaining examples of these instruments and including them in our practice, and I intend to do this and I hope that perhaps other members might consider doing the same.