Nothing is made to the standard that the venerable Denon AVR-5805 was built to but that was an elegant weapon for a more civilized time.
see:
https://www.audioholics.com/av-receiver-reviews/denon-avr-5805
I wept when I had to sell this unit and then I wept again when I had to give up my Denon AVP and POA Separates since there was no upgrade path to Atmos or HDMI 2.0.
The AVR-X8500H is the closest thing you're going to get from Denon these days to the AVR-5805 as it's built in the same production facility in Japan that the AVR-5805 was made. It was also designed by the same brilliant engineer.
I haven't heard of many failures of new Denon receivers. You do have to be very careful to make sure you have a stable wired ethernet connection when doing firmware updates. I NEVER do firmware updates wirelessly. Perhaps there was a hiccup during the upgrade process that lead to the failure you're seeing.
Before throwing it into the kitty litter box, give a 2nd unit a try.
I'm running a Marantz SR8012 in my family room system in a 5.2.4 speaker configuration and very pleased with it. Good luck.
PS. I never reviewed the Yamaha AI feature yet. That was a preview article. I am running a CX-A5100 processor in my theater room and will be upgrading to the CX-A5200 next year to test it out. The AVENTAGE processor has excellent build quality and is well worth it's asking price IF you're ok with only 11CH processing.