There doesn’t need to be a huge overarching plot. Like I said the earlier seasons I enjoyed.
For me personally, the overarching plot was what garnered my interest. Unlike the episodic format of the X-Files--though, it did have overarching plot points as it concerned Mulder and Scully--Fringe's focus on Olivia, Peter, and Walter--i.e. Olivia with Cortexiphan (which is a nod to the MK Ultra Program,) Peter's being from an alternate universe, and Walter and William Bell's conflicting applications of their "intellectual supremacy"--was what kept me engaged. It almost had a comic book feel to it, while carefully staying away from the tropes. If there were a reboot, I'd give it a chance, but I honestly don't know what more they could do especially since the show broached the subject of multiple universes and multiple timelines during its run.