Again, users are unrealistic in their expectations.
Duelyst comes from a relatively (more like unknown) studio. It's art direction, while retro (and retro is in vogue atm) is not appealing to the market at large.
They have less money than most of their competitors and despite being one of the first non HS ccg's on the market to make a push for second place have been slow to release additional content and still have no clear deadline as to a mobile release while direct competitor's such as Shadowverse prioritized mobile even before their steam release.
New kid on the block, Gwent IS well funded, comes with huge name recognition and extremely polished and drawing big names such as Mogwai and bigger names from HS such as Lifecoach as content creators.
By emulating popular elements from HS, Duelyst went for a short term gain at the expense of features which made it unique to the market, it's board.
This in turn opened the door to project's such as the up and coming Shardbound to be able to promote themselves as the future of tactical board based ccg's, something Duelyst no longer will be able to hold on to. Not to mention the only competitive player to ever (as to my knowledge) receive a sponsorship in Duelyst, Nick, The Scientist has since moved on to Shardbound and the game can do little worse than to pick the minds of players such as him, solafid and a host of disillusioned ex Duelyst players.
Ultimately my opinion is that it's extremely unlikely that Duelyst ever becomes "big" in the sense that it's players might have wanted it to, but with proper balancing and a genuine push for new content I don't see why it couldn't at least be competitive and a niche gem in the market that would be a credit to CP when trying to attract funds for future ventures.