I honestly don't understand why people are complaining that the pacing is too slow. By this point in XY, Ash only had one badge, and Serena didn't even know what she wanted to do. It's not like they got to the plot immediately there. :/ And as Janovy mentioned, at least in SM, we've already got some foreshadowing with Tapu Koko's interest in Ash and whatever traumatized Lillie so much that she can't even touch Pokemon, not to mention that photo of Lusamine and Gladion in SM08 indicates that they're going to show up at some point, which is more than what we got in XY during the same timespan.
Really, the pacing here isn't that much different from the other series. Only real differences seem to be that Ash had more Pokemon, and for the most part, the side characters had clearly defined goals. And really, those are my only complaints about the series currently. After the events of SM12, Ash needs another Pokemon. Immediately. And for all we know, SM15 and 16 may very well be capture episodes (we know nothing about SM15-17 aside from a brief paragraph of summary each, after all). I also think the side characters besides Lillie need more focus, but that will probably come in time.