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Seriously, it's not about the mechanics.  It's not about whether monks have d8 HD or d4, whether wizards have to memorize spells slot for slot or get a pool of spells known for the day, whether fighters learn improved trip as a feat or as a maneuver. It's not about whether use rope is on the skill list, and whether hit dice are rolled and constant or unrolled and scaling.  Those are details.  Some of them may even be important details, but they're just details.  It's about the way the game plays.  Even the details that are important are only important insofar as they effect the way the game plays.

Next is like pre-WotC D&D in that there is an emphasis on speed of play, and on DM adjudication over heavy codification.

Next is like 3.x in that there is a lot more codification than pre-WotC, a lot more character customization.

It's a lot like pre-4e generally in that the game is balanced around the adventuring day, there is a lot more tolerance for imbalances (and I don't mean different power structures) across pillars, levels, days, and encounters.

It's like it's own game in the attempt at flatter math and bounded accuracy, and insofar as it's taking a middle-ground approach.

It's like 4e in that, well, actually it isn't anything like 4e at all.  A couple of details are similar, like at-wills, HD, and monster design. But in broad strokes, it's nothing at all like 4e.  4e was balanced around the encounter, focused on tactical combat with meaningful options for everyone, and more or less balanced (granted you could make crap builds and awesome builds, but you could make an awesome build of any class that was more or less equal to an awesome build of any other class at any level).  Next has none of those things.  It doesn't play anything like 4e, it doesn't run anything like 4e.  Roles, AEDU, and surges helped 4e get where it was going, but Next isn't nothing like 4e because it doesn't have those mechanics it is nothing like 4e because it hasn't achieved those goals (some purposefully, others just by accident).  

Maybe you didn't like 4e and you think that's a good thing.  Maybe you liked 4e but you like Next too.  I'm happy to admit there was plenty not to like about 4e and that even the goals 4e was working towards weren't for everyone.  But asking how many mechanics it's borrowed from 4e relative to 3.x/pre-WotC is entirely missing the point.  It's not about where they cannabalized the parts from, it's about what they're building with them.  What they're building is a new game, but it isn't "not 3.75" because of mechanical pieces that are new or borrowed from 4e, and it certainly isn't "not 3.75" because 3.x itself borrowed many of it's mechanics from pre-wotc editions.  It's not 3.75 because it's quick, because you don't have to be trained to participate, and because there's a lot more room for DM judgment calls.  If I had to place it on a spectrum I would call it 2.5, but that's got nothing to do with some kind of average of its mechanical sources.