People need to remember that the majority of voice acting isn't a stable income, and the switch to new actors means other people lost work on something they would rightfully believe to have been a guaranteed job. No one likes it when they're suddenly replaced without warning. While Quinton Flynn retweeting posts can be shitty, he was also essentially stabbed in heart by being removed from not just from a job, but from a character he's very attached to.
This, and already aren't some of the original talents old? This project could very well span for a decade, maybe even a bit more.
In that case, every single actor in Kingdom Hearts, a franchise that'll span far longer than FFVIIR, should be replaced immediately. They could keel over any second! In fact, everyone above 35 should just be forbidden from working all together.
Don't get me wrong, I understand where you are coming from, but it's not like these people are in their 90s. The only one I can think of when being concerned about age is Beau Billingslea, who's in his 70s now.
Also, being young isn't a guarantee they'll be around throughout all of FFVIIR either.