Why did they change all the voice actors?

[Laraul]

With American cartoons the actors don't get anything, because, the industry as a whole, thinks they didn't do much, just lend a voice.

Each voice actor on "The Simpsons" gets $300,000 per episode. Movies such as the Pixar's "Inside Out" feature the voices of Amy Poehler, Mindy Kaling, and Lewis Black, all who are able to demand a $7+ figure salary for a single film.

The English voice acting is actually pretty good, IMO. Each character's voice adequately fits there persona, and they show a range of emotions. What I think people don't like is the some of the old english style dialog, long cinematic cutscenes where there's a lot of speech but not all that much is said to advance the plot, and just the tediousness of the cutscenes themselves.

Overall which is better? Japanese or English? That's a matter of opinion. But I'm going to guess that plenty of people ranting that the Japanese voice acting is so much better do so because they've seen a few dubbed anime with cheesy voice acting, and then assumed that's that the rule, not the exception, and made up their mind before giving the english voice overs a chance.