I just want to know what the auditions were like, and how they came to decide on these actors among others. We don't know who the casting director is, and the thought-process behind casting tends to start with the screenwriter. They typically write characters based on a certain actor (or two) in mind, and they cross their fingers and hope the person agrees to play the character. If they don't, they go looking for someone else who is similar, but they may have to make some tweaks to the character in the process.
Shrek is a good example of this happening. Chris Farley was the go-to choice for Shrek, and the character was originally written for Chris. When he died before he could finish recording, they went with Mike Myers since he's kinda similar to Chris, but Shrek had to be rewritten to fit Mike (I think that was Mike's idea out of respect for Chris). The Genie is an example of it going right in that Robin Williams wasn't a guarantee, but he loved what the animators had put together in their reel for him and agreed--but then the marketing manipulation upset Robin. Dan Castellaneta was a fine replacement for Genie in the TV series and the character didn't need to be changed for his comfort, but he didn't have quite the same manic energy as Robin.
So however the auditions went, or if these were the de-facto faces for the characters, it's indeed a very baffling choice, but I would hope that they can disguise their voices into the characters. Yeah, not every actor can do voice-acting, but if they're able to lose themselves into a character on-screen, you can trust they can lose themselves in an animated character, as long as the ADR director is competent. I regrettably have to give Illumination this that they at least have a sense of good voice-directing in their projects. The movies still suck ass in presentation, but off the top of my head I can't think of a truly bad voice. (Yeah, you can say that having generic/average voice-actors is still just as bad, but they blend in to everything else in this bland world of entertainment at this point that it's to be expected.)
Chris Pratt has experience in voice-acting, I just don't know if he's able to put on a convincing Italian accent because far as I know, he's never proven that on audio. Jack Black has more experience than him in that regard, but the last villain I can think of he voiced (he's been a villain on-camera before) was Zeke from Ice Age, and that was long before he got household famous. I don't even know if he can deepen his voice enough to pull off a convincing Bowser, but he at least has the ham down-pat.
I have no fucking idea who Anya Taylor Joy even is, never heard of her before nor seen anything she's been in, but honestly, Peach can sound her typical sugary sweet (Peeee-chee~), or have the mature voice of Leslie Swan in Super Mario 64. Any woman who's not a chain-smoker I think can voice her. Everyone else minus Kevin is a make-or-break it at this point, with Seth Rogen potentially being the worst of the bunch just due to him being everywhere at this point. (I've never watched the Smurfs movie so if Fred Armisen was awful in there as Brainy Smurf, then hold on to your butts.)
I want to be pleasantly surprised, but I'm bracing for the worst for when the first trailer will drop.