George is correct. Lack of switching bandwidth is the problem. I know Bruno Putzeys claimed differently in an old interview, but he's mostly a self-promotor so no one should take what he says as gospel truth.
For the record, Bruno Putzeys is the one that made self-oscillating class D amplifiers a reality, a practical thing. That's a pretty big deal; if you work out the math for that you are doing quite well. You better be good at calculus with multiple variables! He also is able to show the measurements to back up what he says about how the technology works. Attacking Bruno is really done at your own peril!
By 'switching bandwidth' I think you must mean 'switching frequency' since 'switching bandwidth' isn't a thing. And in this regard your statement is false. Based on the rest of your comments I would venture that you simply haven't heard everything that's out there, and just like traditional solid state amps and tube amps, there is a tremendous variance in class D implementation!
You might think of it this way: digital has come a long ways since 1981 when it first started showing up. Its common now to see scan frequencies of 192KHz; class D amps are commonly switching well over double of that. At the current state of affairs, the practical upper limit is around 600-700KHz before you really start to get into troubles with radiation and oscillation issues- the fact that Technics seems to have gone well past that says a lot about their engineering expertise. But Technics has to switch faster, since (if their claims are correct) their circuit is zero feedback, so they have to raise their filter frequency quite a lot in order to avoid phase shift at audio frequencies. Also for the record, self oscillating class D amps don't have to do this- their filter frequency can be lower since they can run so much feedback that it is able to correct for phase shift.
@tweak1 Thanks for your offer!