I am going to argue that Abyss' characters were not obnoxious (maybe Anise and early Luke were, but even they weren't that bad) and that the technology talk wasn't even remotely cumbersome. The first time you hear a term it may confuse you, but after that it's extremely easy to pick up and adds to the experience. It added a sense of immersion for me at least.
I don't want to compare to Vesperia since I haven't played it, but I wouldn't call Abyss out on problems that weren't even that major.
Mieu's voice acting oscillates been grating and, "so-bad-it's good." As for the fonons and the Score and the rest of the lore, I believe it is too much. At the very least, too much information is piled on in the first arc. I appreciate the game taking the time to really flesh out its universe, but it needed to do it at a slower pace. The game doesn't even try to hide how dense its lore is - the main character was made purposely oblivious so that the devs could explain the basics over and over.
In any case, Vesperia is less lore-heavy. That is to say, most of the conflict in game concerns on-going events that do not require a context of fictional history. Abyss definitely built the more expansive world, fonons and all.