I think your basic assertion that "hard material" tweeters made from a variety of metals are often a bit much in their presentation of treble and how they integrate with the other drivers in a particular speaker design is on point.
Soft domes, as you assert, do generally have a more forgiving nature.
In my personal experience, my circa 1980s Vandersteen 2C with their soft silk dome tweeters, had that more musically satisfying treble presentation than the metal domes in all iterations of the Model 3. The 3A Signature in current production have come a very long way toward providing treble detail with smoothness of response.
My current Treo CTs have a literal seamlessness between drivers. Once you have them set up properly, you just listen to music and really don't think about the relative contributions of individual drivers. Amazing accomplishment for Richard Vandersteen!

