I'll take mid or low tier voice acting over AI generated voices any day. I'd much rather listen to a poor voice actor doing their best than a robot voice that has the emotional depth of, well, a robot. Maybe it's just me, but whenever I hear AI voices in a game it immediately takes me out of any kind of immersion. I'd honestly take no voice acting at all and have it be all text over AI voices. And for story related characters I'd find it near impossible to relate or empathize with a character that literally has no part of it that even resembles a real person. I can kinda see what you mean with no-name NPCs that have repeating voice lines, but in a big open world game what would the standards be to consider a character important enough to have human representation? If the dialog isn't important and will be ignored most of the time, why do you even need it in the first place?

In Arc Raiders, all of the voice acting is AI generated and it sounds okay at best. It creates a problem that puts your main characters on par with the guards in Skyrim where most people ignore them. I played it with a friend of mine and ended up skipping 90% of any the dialog because I found it tedious to listen to.