In a word? No.
I played through White twice. It was easily one of the best games in the franchise based on story and production value, and it was very clearly a step in the right direction in terms of writing, but at the same time, there's one major, major flaw:
It was same-old, same-old.
You start on a journey from a small town, get a starter Pokémon from a professor, then get set out on a journey to complete the Pokédex, and you go around beating the gym leaders to collect badges to be able to dethrone a champion. The fortunate side of this is that the villains actually gave you motivation to do this, as opposed to just being annoying enemies that got in your way from doing it. The climax was also far more interesting, obviously, so that's a step forward. BW2, although it starts in a city and you get the starter from Bianca (not spoilers because it's first ten minutes lol), is the same after that.
The WORST instance of sameness, though, is the battle system. It hasn't changed at all since Gen III! That's nearly TEN YEARS AGO. In Hoenn, we got abilities, natures, and double battles - all of which significantly changed the scope of the battle system, and gave us something new to play with, new things to discover, etc. In Sinnoh, we didn't get anything new, just the physical/special split that basically changed which moves work well on which Pokémon. In Unova, what did we get? The sporadically-used triple and rotation battles and 156 new Pokémon?
Look at other franchises, like Final Fantasy or Tales. With every game, they have a similar battle system (although Final Fantasy has changed in recent years), but they make tweaks. They make changes. They take the same basic system and make it different every time, with various customizations like spheres in FFVII or fon slots in Tales of the Abyss, and things like Fields of Fonons made the game have something different than its predecessor. Pokémon doesn't have anything like that. It's the same damn battle system every time, just with a new region, new Pokémon, new abilities, new moves, new hold items, etc.
Do other series always have new regions with more places to explore? Yes.
Do other series add new enemies, abilities, moves, and items every time? Yes.
Do other series change the fundamentals of the battle system more frequently? Yes.
That last one is what gets me. Pokémon is indeed dying because they can't give us new core gameplay mechanics. All they do is pump in new things to the same-old, same-old. A new ability that's going to be put in play 20% of the time won't make a difference. A new attack is basically just a variant of an old one, just with different typing or a different side effect. New hold items aren't going to mean a thing, they just add another choice to the SAME-OLD, SAME-OLD.
What Pokémon really needed with Gen V is something new gameplay-wise. They haven't given any dramatic changes in ten years. Like I said, the physical/special split was a more realistic system that simply changed which moves worked on which Pokémon. All they're doing is making subtle enhancements that make our lives easier and give us more time to focus on the task at hand, which is nice. But it's the same exact battle system we experienced in Hoenn, just with more stuff to keep track of.
They really need to go the real-time route, because turn-based RPGs are dying, and that's because of Pokémon. They have exhausted their own genre. It just isn't fun anymore. White was simply a means to pass the time and enjoy a darker plot for a series that needed it. Now let's hope they give us a major shake-up like customizable moves (such as using an item [not holding one] to increase the chance of side effects or to increase a move's power by 10%), combo attacks (like combine Flamethrower with Ice Beam to create a "Fire and Ice" attack), or a real-time system where you can control your own freaking Pokémon.
Black and White weren't a big step in any departments but story and polish, and although the protagonists were both well-designed, a good amount of the other characters were not. They have a lot of work to do if they want to get me to buy a Gen VI game. I haven't even gotten White2 yet, and I don't know if I want to. It would at least be nice to contribute a harder difficulty that you don't have to hack to unlock (being in my 20s, there aren't many others I know who play Pokemon and could give me it).
So, to answer your question, Black and White really weren't a significant step. We need it badly, else Pokémon isn't going to have much steam left in five years.