You're invalidating the new VA's talent when they've accomplished the incredible feat of smoothly subbing in for such an iconic voice and even if they don't have identical pitch, tone, modulation etc (and they won't because they're two different human beings) it's obvious they're incredibly talented, just listen to that last add with Mario on the pipe, it's charming, magical and endearing just as Mario is supposed to be and you can't expect people to take you seriously when you discredit a professional like that in favor of hiring amateur Twitter impersonators with limited range because of no real experience with voice acting.
You can criticize Nintendo all you want, but a bad take will warrant bad reactions.
If I were the only individual on the planet criticising the voice, you might have a point, but alas we're not in going to be in agreement that they're 'smoothly subbing in'. You even said that It sounded 'identical' to Martinet which is just plain nonsense. I will agree that single ad is probably one of the best takes because it's mostly just simple quick sounds, which this VA is best at. The line at the start however is very obviously not similar. Nintendo didn't even bother saying anything about a VA change when Wonder was revealed, it only happened after people noticed and began to question something was up. Makes me wonder if they were hoping for the transition to go more smoothly, or if they were waiting until the game was actually out and had to abort that plan, but that's just speculation without hard evidence; I won't delve much into it.
Whether they're talented or not is irrelevant here, it's about if they're the right pick for the role. Is Matt Mercer talented? Sure, he's done good work. Was he the right role for Gannondorf? Very debatable because his voice just doesn't suit the character he's trying to portray. He's a younger guy trying to do an older sounding voice, and it can be heard. Whether that was the direction he was given or his own take on Dorf doesn't really matter. With Zelda, she sounds like a North American trying to put on a British accent. I'm sure she's very talented as well, but she clearly wasn't the best choice for that role if they wanted an English regal sounding Zelda.
Your last comment about the Twitter impersonators is also quite frankly pure nonsense. We know Martinet has a huge range even solely as Mario and any impersonator who can replicate all of that (even if just specific to Mario) is more than sufficient to do the job. Handwaving away a lack of experience (?) is again, nonsense. Some of these Twitter impersonators also work in a professional capacity by doing commissions or are just general voice actors.
The only part I'd be in agreement with is that not all Mario impersonators make good Luigi ones (I will say out of the few clips I've heard so far I think he makes a better Luigi than Mario), and so Nintendo would likely have to do multiple castings instead of just one guy. They were very lucky that Martinet had such a wide range to voice all those characters in the past. Even getting a 'professional' in your words to do all of those seamlessly is going to be an impossible task.
People might say you can criticise Nintendo here, but all references were to business practices or their online services. Criticise the games and the mobs show up.
A recent example of a popular recast with similar issues would be Rick and Morty. Whoever they've hired to do both or just one each has done a sublime job of Morty. It's almost spot on from the trailer. The Rick? Not a great choice at all. When he raises his voice especially he just sounds nothing like Rick. Considering they got a perfect Morty it stands out even more.