It doesn't matter if it far behind, or close to the competition. It's behind and gamers also like to benchmark and show off where they spend $500-$700. So if they are not big fans of AMD, they will go with the Nvidia option. AMD knows that and as a company that tries to make money, it will not start giving away hardware at single digit, or zero, or even negative profit margins. They are not Intel to start throwing billions in an effort to maintain a market share, or get into a new market.
Vega was meant for professionals. Koduri probably was hoping to get 1.7GHz or more out of it, without first getting in the "extremely bad efficiency" territory. It couldn't be done, so it wasn't the gaming card many where hopping to be. Not being fast enough meant "1080 price range" not "1080 Ti price range". And that was the end of it. The only way to promote it was as a package with a Freesync monitor against an Nvidia card and the much more expensive GSync version of the same monitor.
As for Vega's technologies. Not going to happen. When you don't feel/want/need to sell cards to gamers, you don't throw money into Vega's specific technologies. At least not as much as you should. And even then, if Vega needs special programming to beat Nvidia GTX 1080 without Gameworks and stuff, that's bad. There where articles a few weeks ago about primitive shaders support getting canceled. Also if you see how badly RX 400 series and Fury cards are getting beaten from RX 500 series cards, it's obvious that AMD is starting to follow Nvidia's manual here." Optimize only for the latest series".
AMD will sell to miners and professionals because they don;t have to invest more money to do so. They can't sell to gamers and they aren't going to try selling to gamers because it is too expensive(low price for the cards, plenty of dollars to developers to optimize their games for GCN).
You are NOT going to believe this, but I am FULL AMD. Just prefer to be realistic when expressing an opinion. You have to realize that you own phrase "a Vega over a 1080" shows the problem. There is NO "Ti" in that phrase.
One more thing, then I will stop it, really xD You should look through some numbers before claiming the 580 is beating the fury (Not meant offensive btw. maybe you got other numbers than I did). In DX11 you are right in a few cases but in DX12 and Vulkan it's an entirely different story. http://www.guru3d.com/articles_pages/amd_radeon_rx_vega_64_8gb_review,13.html (might be a Vega review but they also got the 580 and Fury / X involved). The Fury / X is a good bit faster in nearly any szenario.