I finished almost all the routes... but I left Carl's route aside because I thought it wouldn't make much difference in the story, maybe I should play it? my sequence was: Leo, Jenna, TJ and Flynn
In my opinion, Carl's route is either a hit or miss. Without going into spoilers, it's drastically different from the other routes. So you're right, it doesn't make much difference in the story, and that can be good or bad depending on preferences and expectations. Personally, I enjoyed it initially (being the first route I played), but after replaying the entire game, it's not as good as I remember.
But don't let the opinion of this stranger deter you from enjoying more of Echo, it's ultimately up to you!