OK, lets look at the 'facts' on VEGA:
-Availability is practically non existent, with what few cards that are available going for hundreds of dollars above MSRP. This is resulting in vega 56 cards, which compete with 1070 performance wise, selling for almost 1080ti money.
-Power consumption is very poor compared to pascal, abysmal for vega 64.
-Overclocking headroom is very poor
-Third party cards have taken more then a quarter and are still not available to purchase
As a result of lack of coolers and high power usage, cards run hot
-Performance of vega 56 is competitive with 1070, vega 64 is close to 1080.
So, objectively, VEGA fails abysmally on price, availability, power consumption, heat, and cooler variety. The ONLY way it is remotely competitive is absolute performance, but given it falls so far behind on all other fronts, it is hardly a "competitive" chip. A chip that fails at every metric except outright performance many will consider 'garbage'. especially when you also consider how late to the game VEGA was, over a year after pascal came out, and the fact that pascal, despite being locked down, has *more* OC headroom then VEGA does. .
At MSRP, Vega 56 is a good card. At the 'promotional' bait and switch price, Vega 64 is a good card. But neither card has been commonly available anywhere near this price, and that situation will continue for the foreseeable future. By the time AMD has fixed this problem (if they even bother) volta will be out, and AMD will be 1+ generations behind yet again. Calling the GPUs themselves garbage is debatable, especially given vega 56, but calling the arch in general garbage seems to perfectly fit its situation.