That's somewhat contradictory. Saying they were competing in the high end means they did have in fact a comparable product. It is difficult to create a lot of mindshare and not even Nvidia has done it in one go, it took years to get to this point.
Comparable and very strong, both abstract but definitely a difference there
I'd say Hawaii was comparable, Fury X was comparable, but Tahiti was 'strong'. It had great balance and it offered something the competition lacked with its 3GB VRAM and wide bus plus a lot of core grunt; it was really GCN in its sweet spot. Nvidia's 680 wasn't really enough to eclipse it, and it was the best they had until Kepler refresh (discounting the 1K$ Titan).
It is also the 7970 that created the fabled 'fine wine' argument because this GPU was released with meagre driver support but can still play ball today with much improved performance. If we talk about mindshare, that GPU on its own, along with the 7950 as a poor man's alternative, has done more for AMD than the past three refresh gens combined.
If there is one universal truth about mindshare it is that you cannot gain any of it with midrange or entry level GPUs. Proof: everything Intel has done on GPU, and everything AMD has done in the past few years. Its like a Dacia car, you know it drives alright and you know its cheap but you also know it won't break any records and that every opportunity to cut corners has been taken. Its the car you buy because you can't afford anything else. That is kind of where Polaris is at right now. In the meantime, Nvidia is selling BMW's even if they are just 1.1 city cars with a shitty engine ie. cut down GP104's with clocked down GDDR5X. And they can only call them a BMW because they've got that M5 model at the very top breaking records.
Sorry for the crappy car analogy, but I couldn't think of anything better
Nvidia mindshare kind of exploded when they released Titan. The card nobody in their right mind would buy, but when they cut it down into a poor man's version with the 780, we jumped on it, and they enabled themselves a new tier and price point for high end GPU. That is why today some people consider a 104 die 'mid range' when even Nvidia says its a high end segment SKU. Prior to Titan, both competitors tried similar tricks with dual GPU solutions like the 690 and 290X2.