I think it shows pretty obviously that Newer DS benefits from years of additional insight when it comes to level design, and the NSMB DS engine (and how much mileage the Newer team gets out of it) lends itself better to these kinds of traditional-with-a-twist levels than what Wii had.

Simply put? It's a pretty good Mario game! Just like the last one, some of its strongest levels are genuinely clever.
But it's also an amateur one still - star coins often don't know how to run a happy medium between painfully formulaic and excruciatingly obtuse, for example.

I imagine this would be what it'd be like if I tried to create a Mario game after a few months, maybe a few years of studying the series' levels. Decently thought out in theory, but a bit by-the-book in areas where I probably would deviate from the norm would I know exactly how to.

It's still better than Super Mario Maker.