I had no idea Denon was related to Onkyo :)
I was however surprised to learn that Denon was actually founded by an American in Japan in 1910.
Given all this, I would find "obsolete" a misleading descriptor. For that matter, I'd find "traditional" misleading as well, as that could refer to the native Japanese pronunciation (kun'yomi).
The market segment for Onkyo just doesn’t exist anymore - those that want receivers and a HiFi/HT setup are already well served Denon/Marantz and Yamaha (and the “audiophile” world beyond that is a pretty well saturated market). Sony is still around but that’s clearly not their core business.
But the former Onkyo base has been eroded by soundbars and wireless multi speaker setups.