2070 is garbage. Different, but still garbage. You can't land battle, which makes taking over islands more of a pain in the ass because they tend to be too wide to do much with boats. Planes go down quickly. You're just not encouraged to take more than one island, which restricts gameplay.
I wouldn't call it garbage. I hadn't played anything else in the series but I've put in 270 hours into 2070. That's 270 entertaining hours: I did not find any of that to be a grind.
I agree that military conquest is annoying since you definitely need planes and they are expensive and weak, and the only way to beat an AI opponent militarily is to keep the pressure up because they don't actually have an economy that you can cripple in order to wittle them away: they simply rebuild their buildings following the same pattern (based on their faction), regardless of whether it even makes sense to build a dozen oil derricks or coal extractors on an island with no oil and depleted coal stocks.
That said, none of the campaign missions require that you obliterate an enemy's island presence completely. There are a couple challenges maps (slash achievements) that do require it, and of those, I had only had difficulty with one of them (to the extent that I looked up a "recommended strategy" to win it) when trying to play in my usual inefficient manner.
Even if the military game sucks, I felt the rest of the game was extremely good. So good that I'd love to see more of this industry/economy type management game; in fact, I'd love to see that whole economy model adopted into late-development DF as an extension of civ-level management (the whole extract resources, refine resources, produce goods, refine goods, produce better goods, refine better goods, etc). In particular, I think it's an opportunity to look at how consumption can work in DF for non-food/drink items (the civ/worker population in Anno consume luxuries in addition to food and drink, and more skilled workers require varieties of increasingly "complex-to-produce" luxuries/food/drink in order to be satisfied).
I strongly recommend it as a game, if you enjoy the management aspects of DF, or other management games like Sim City. The major gameplay is definitely in the satisfaction of designing and building up a well-running colony. It also did something very well (and rare these days) in that most, if not all, of the achievements actually unlock more things, which give you goals to work for despite the freeform gameplay outside if the campaigns. I felt there were more things they could have to add additional late/top-level gameplay (for example, a by-territory world map for establishing other colonies, sort of like Dawn of War:Soulstorm or Empire:Battle for Dune), and the multiplayer aspect is decidedly unrewarding, but nonetheless what's there is a complete game in its own right.
However, it is still a ubisoft product. In addition to the restrictive licensing mentioned earlier, it also require Uplay, which is Ubisoft's steam/origin clone/launcher. I wasn't aware of that when I first bought it (too lazy to Read Everything) and knowing that now makes me even less inclined to buy ubisoft products, but it hasn't caused me any significant irritation to the extent that I'd rather not have bought 2070.