Abby and Connor just don't cut it as the stars of the show.
A couple seasons ago when Cutter was temporarily MIA Lester dryly remarked that the two of them leading the team was like Scooby-Doo and Velma in action. Well that works as well for them as show-leaders. The comic relief characters just don't work as the focus.
I miss Cutter.
btw, did they ever resolve the inconvenience of this being a new timeline for Earth? A different personality Lucy Brown et al.