Well, to start... AI means Artificial Intelligence. Meaning, "the ability of a digital computer or computer-controlled robot to perform tasks commonly associated with intelligent beings." This would imply that even the voices aren't real, that the Mave members are simply computer programs with a mind of their own, and that's not what Mave is. And it's important to make that distinction because there's a difference between being an AI group and what they actually are.
Mave is a group where instead of you seeing the real singers, you're seeing a CGI model in their place. Everything else comes from a human being. It's the exact same as a VTuber who sings, only Mave has a MUCH higher budget than your average Vtuber. Think of Aespa, but imagine if instead of them having the four members plus the Ae-Member concept, it's only the Ae-Members BUT Ningning, Winter, Karina and Giselle are providing the voices and motion capture. Or KDA, but unrelated to any previous media and you don't know the faces behind the CGI models.
As for people being skeptical... I wouldn't write it off so quickly. After all, Vocaloid has been around for YEARS, and Vocaloid is a series vocal banks that producers can use to create their own songs. People have been making Miku songs from at least as early as 2008. I think this was inevitable with how technology is becoming even more ambitious, the pandemic just made it come quicker. Will it replace human creativity? I certainly don't think so. At least -- not yet. I think we're still a ways off. But, this could be a way for companies to debut singers that may not have the right "looks" to succeed but have the skills that are too good to waste. Or for those who have anxiety, but still want to be an idol. They can use it to cut costs for certain things such as transportation, there's way less risk of scandals occurring between the members, and if a member needs to go on hiatus/leaves the group, they can find a replacement easier compared to how risky of a situation that'd be for a typical idol group.
People liked KDA. Whether it's because of League or because of the amazing notable voices behind the characters, what made people stay is the music. In the end, that's all that matters. If the music is incredible, people WILL tune in, even if the concept is something they're not used to. But they have to nail the execution and going off what I'm seeing, I think they know what they're doing. It's not going to replace human idols, and that's not the intention. With this, you now have the option of having both Virtual AND Real idols. But will it be a successful idea? We'll have to see.