Or am I getting something wrong?
Not 'wrong', but perhaps incomplete.
D&D Next came about because 4e wasn't selling as well as WotC expected, and because Pathfinder's sales growth made it appear as if 4e might soon be pushed into second place. There are radically different explanations for why these things happened, with some blaming bad decisions and unrealistic expectations at WotC for torpedoing an objectively strong 4e ruleset, and others seeing 4e as a highly flawed ruleset that may have achieved greater balance but did so by dumbing down the game and removing the flavor that made D&D special. Many people have sincere and strongly held opinions about which view is correct, but for purposes of this thread, who is "right" isn't important. It's the end result that matters: the natural D&D gaming community splintered, leaving 4e with a smaller fanbase than WotC was willing to service.
Next was introduced as a way to claw back market share and reunify the splintered role-playing community. The idea was that useful and meaningful elements from each edition could be combined into a coherent whole, so that fans of any edition could "feel like" it's their own edition even though the mechanics would not be identical to any edition that's come before.
Whether this is doable is an open question. Many people in my 4e gaming group see 3e/Pathfinder fans as balance-hating grognards who want to "roll back the clock" to an overly complicated and objectively broken ruleset. On the other hand, many people in my 3e gaming group see 4e fans as flavor-hating dullards who want to re-enact Diablo on their battlemats rather than play a real RPG. And if each group really were as the other describes, then I would agree that it just isn't possible to produce a Next that can please both, because 4e players won't sacrifice balance and 3e players won't sacrifice richness and flavor.
But I think neither side is correct. I think 3e fans do value balance, but don't like the highly standardized manner in which 4e achieved it, which may perhaps have inadvertently removed much of past editions' flavor. And I think 4e fans do value richness and flavor (and are every bit as smart as their 3e counterparts), but don't like the balance and complexity issues that were perhaps allowed to persist in 3e in the name of richness and flavor. This leads me to believe that a less standardized yet well-balanced system, that restores past flavor without needless complexity, can perhaps do exactly what WotC says it hopes to achieve.
If Next really were nothing more than 3.75, then I would agree that it's doomed to failure -- and I initially shared your suspicition that this is exactly what WotC would do. But I see more than this when I play Next. Many of my favorite 4e design elements, like themes and backgrounds and at-wills, have made their way into the ruleset. Some fondly remembered flavor from 1e and 2e is there as well, along with the more freewheeling style those editions so often represented. To be sure, some 3e elements are present as well, but I don't personally see that it "feels" more like 3e than the others.
I'm sure those who insist that their edition represents the pinnacle of D&D won't be satisfied with Next no matter how well it achieves its objectives. But for the rest of us who just want something that can restore our splintered gaming tables and let people hang out and have fun, Next represents a promising possibility, though only time will tell whether the 5e team can turn than promise into reality.