So... why were they flying off the self in the olden days? Is it because kids nowadays is all about POWER POWER AND MOAR POWER, and they don't care about timing and good technique?
Any of us who play (or played with one for extended amount of time) know Prestige Mid is a wonderful racquet. And if you've got the strokes, it's just like any other racquets.
Of course I can't give you hard evidence favoring my hypothesis, but I'd say that rackets such as the Mid sold well in the past because many (top) tour players were playing with it (resp. the various iterations). Today rec players don't get to see the Prestige Mid very often on tour (on the top of my head, I'd say Haase and Kamke are the only players using a Prestige Mid in the top 100, are there others? And if so, they're nowhere near as popular as the guys at the top.)
So people are more inclined to buy what they see, plus what's marketed by the companies. Do you see ads for the Prestige Mid? Heck, Head even didn't "dare" to make the 25th anniversary Prestige a Mid. Probably because they assumed that it wouldn't sell as well as a MidPlus. - If that's actually true is another question, of course.
And (most) people will fare better using a racket like a 100 squin Speed, for instance, compared to the small Prestige Mid. Simply because it's easier and allows for a larger margin of error. And if you try to emulate the "modern" game, you'll need a lot of margin
When I was playing as a teenager, I loved my Prestige Mid (I had the second gen Prestige Pro and the first Prestige 600 back then. Unfortunately, both were thrown away by my mom in a house cleaning operation literally just weeks before I found my love for the game again, but at least I was able to save the rest of my old equipment. If only I had stored the Prestiges in the attic...). But I personally wouldn't touch the racket today and prefer my Radicals when it comes to Head rackets.