Though they explain why Threes is better in the next line. 2048 is "broken" and easy to beat whereas Threes is a deeper, more challenging game. I think they were trying to get across that they know that Threes is a better game because they spent over a year working out the design and ensuring that they didn't make a "broken" game like 2048.
But this exposes an underlying assumption in their thinking, which is that a deeper game is automatically a better game. I would argue that this assumption is mistaken, especially on mobile, where people tend to gravitate towards games they can play in short bursts during downtime. In that context "deeper" just means "harder to pick up and get into."
That's an arguable point, of course, but I just mean that it's not as axiomatic as they make it sound that Threes is better just because it's deeper.
They mention that. "But why is Threes better? It’s better for us, for our goals." and then later: "that’s what’s better to us as game designers. We worked really hard to create a simple game system with interesting complexity that you can play forever."
