Why do they love newbie voice actors so much?

F for Bocchi's VA's carrer

Newbie voice actors > experienced voice actors, newbies performance feels more genuine and energetic than experienced ones.

And they're always good too. Like big names good. Where do they find them/what lab are they cloning them in?

Because, as in all Japanese industries, the seiyuu industry is an iron, flattening out any unique aspect of those who make it up.

Bocchi was C2C though. But is her career really dead?

The best combo is a single newbie in a pivotal role with veterans as the other characters

Examples?

Konosuba for example was Takahashi Rie's first big role. Same thing with Yuuki Takada as Aoba in New Game! and to a lesser extent Hanamori Yumiri playing Nadeshiko in Yuru Camp

>Konosuba for example was Takahashi Rie's first big role
Nope, her first lead role was in Sore ga Seiyuu, and she was also in Gakkou Gurashi and a bunch of other shows before that.

>lesser extent Hanamori Yumiri playing Nadeshiko in Yuru Camp
She already had a singing career and some roles before then.

I said big role, much as i love sore ga seiyuu it nobody watched it. I had forgotten about her role in Gakkou Gurashi though, but you have to agree that Konosuba was her big break

They see the potential in new talent(it's cheap)

KAOS

price and availability

iirc all the other girls in Dumbbell are played by fairly well known VAs, while Hibiki is a complete newb whose only other credited role is a random background extra in One Punch Man