Well, comedic overreactions aside, I didn't enjoy Agito, but it's probably not the show's fault.
I am with you on this one.
I have been watching Agito and while i can tell that it is a good show and there are some really cool things in it, i simply do not enjoy it a all that much.
This is probably due to the fact that after years and years of watching Toku i have developed an immunity to Toshiki Inoue´s writing, so whenever i detect his writing style my brain goes into off mode and just rolls with it without really caring.
That is not to say that Agito is bad, as i said, i can see exactly what people love about it; i had the very same problem with Jetman, logically i can tell that it is a very good show, but it is hard for me to get invested into a dramatic show when my brain literally filters all the tropes that i have come to expect of this autor.
That said, you should rest easy since Nexus is a completely different kind of show.
It is very dramatic, yes, and it is certainly a darker take on Ultraman that introduces some very realistic spins to the franchise, but the drama itself is actually very well handled and it doesn´t rely on absurd coincidences like Inoue´s shows do, not to mention that it actually maintains the themes of Hope and Belief in the Future that characterize the Ultraman Franchise.
Basically, Nexus is an adult and realistic take on Ultraman that keeps the heart of the franchise and treats its audience with respect.
As for Ultraman The Next, while it is true that you do not need to watch it in order to enjoy Nexus, the events of that movie are actually fundamental for a really clever plot twist during the final arc, though most people don´t realize of that since you really need to think about it to get it.
Still, it is a cool movie and it really does complements the Nexus experience.