Atlas IS Ark. They took the Ark engine, changed it to pirate theme on a much larger scale, added an improved sea engine, added much more advanced fighting system, a skill tree that requires specialization, added npcs & stores, and a bunch of other things. Atlas is being built by Grapeshot, which is the sister studio of Wildcard (Ark).
So anything you are doing now in Atlas you will find almost exactly the same mechanics-wise in Ark, except a different theme and not as in-depth melee, as example. But Ark had its falling out too for the first 2 years of early access. As long as players keep thinking early access means finished product, there will always be people upset about constant crashing, bugs, balance, and non existing content as of yet. The good thing about EA is the game companies get player feedback throughout production, which helps them to cater the game to what the players want.
Once Atlas gets its puzzle pieces put together, I can see it being a much better game than ark ever was. There is just still a very long road ahead until it reaches the final goal. Patience is key with games in alpha.
If you haven't seen the roadmap yet for Atlas, would suggest checking it out: