Depending on where in the vicinity of EWR that you live, the path of least resistance may, for better or worse, be just sticking with UA. If you're coming from NJ, the hassle factor alone of getting to LGA/JFK (especially anytime around rush hour) is just such an enormous drag that it wouldn't even be worth switching to an airline with more service out of those airports. On a bad day, EWR is 30 mins for me, and JFK can easily push 2 hours. That disparity alone is worth making UA work for you.

SkyTeam is kinda useless out of EWR - all you've got is DL to hubs (plus randomly BOS/RDU), AF to CDG, and AM to MEX; Oneworld isn't much better (AA domestic to hubs, and a handful of EU airlines). We could get into a broader discussion around airline hub monopolies, but that's a conversation for a different day.