The problem isn't the raw amount of characters. But the focus. In season 1, Tilly appeared in more episodes than Sarek. But only to deliver a few exposition lines and a joke. Sarek got a whole lot of important character moments, and an entire episode focused on him. Something I wish Tilly would have gotten in season 1. Also it's not just the characters, but also concepts. The vast majority of season 1 episodes can be described as either "a Klingon episode" or "a Mirror universe episode". Both concepts that are very familiar and tied to previous shows. Whereas all previous shows usually started with introucing "their" main antagonists and plotlines, and only having Klingons or Romulans appear every once in a while as a change of pace. That's why I prefer DIS season 2 so much over season 1 - even tough the red angel/Conrol-story turned out to have a disappointing ending - it at least is distinctively "DIS", and hasn't been done already (or better) on other shows before!