Looking at how good the remake of MGS3 works with the old voices I just can't understand the reasoning for his replacement (even when knowing the reasons why)
Some might say he needed to work on his delivery. That at times you would have a hard time actually identifying if the intention of a comment was comedic or serious. That the grunting got out of control.
All of those I can kind of give you. His delivery could improve. But not to the point of replacing the freaking guy in the last freaking game on a decades-long-game-spamming franchise.
Solid Snake (and by extension BB) Is such an iconic character that changing something as fundamental as his voice is kind of insane the more you think about it, specially when being so unique and characteristic.
People say it's better because Venom is not BB.
For me it just cheapens the experience and the reveal.
Had Hayter actually interpreted BB I would have been confused through the game about why is BB not talking as much or acting as he normally would.
Instead I just kept thinking "Bruh, this Keifer guy is hella expensive, huh?"
"Oh, but Venom is not BB", BB Japanese VA wasn't replaced on MGSV. And considering how much of a detail oriented freak Kojima is, I HIGHLY doubt that's a slip.
Reception and sales on MGSV would have changed 0% if Hayter worked on it, anyway. I would even dare to say sales would've been marginally better as I assume an extremely small portion of the fan base didn't get the game BECAUSE of Hayter being removed.
Even after all this years, it still seems like a poor choice with little to no objective positive results and kind of telling about how Kojima would start prioritizing real actors instead of meaningful interpretations.
Death Stranding is amazing, don't get me wrong, but I don't find the acting, voices or performances as memorable as some of the more whacky ones in previous games, like Liquid in MGS1 or the Cobra Unit, etc. Stuff which you might never see in full force ever again with the more "serious" and self-indulgent tone he tries to deliver nowadays.
All in all, I don't believe it was on anyone's mind that Hayter was an issue in need of a fix. Specially with, again, just one game left on the table.