Yeah, the characters really aren't being written in all that interesting a manner. I didn't feel the artwork totally fit with the tone of the series either. It's fine art, but it didn't give me a feel of a cosmic plot with big ideas.
I noticed that Lemire is trying to appeal to memories of FF, with Metamorpho (standing in for Ben Grimm) and Plastic Man (who is the defacto Johnny Storm stand-in) arguing with each other, with Mr. Terrific (aka Mr. Fantastic, without the same powers) being the voice of reason.
I found that aspect to be pretty forced. Using ideas that fans think of with the FF is perfectly appealing (exploring the Multiverse, etc.), but trying to make it so that random DC characters are simple archetypes of the Lee and Kirby creations is really trying to push matters too far.
However, I did read most of Dark Nights: Metal, so maybe the comic works better being familiar with the prior material.
Lemire isn't always at his best working with established superhero characters. His work at Marvel was very hit or miss, and let's not forget the horrible mess of his Justice League Dark and (brief) run on Constantine. His creator owned work has always been some of the best work being done in comics at the time though.
I think Terrifics may have possibilities and am willing to stick with it longer, as not all of Lemire's "mainstream" work ends up as a failure.