I agree and disagree. Yes, it's not Pavarotti BUT it's a certain sound and persona people grow to like. They replaced Bon Scott with Brian Johnson a LONG time ago. They had no choice, Bon died. I do remember that, and at the time I did not like Brian that much. He still sounded good but I wasn't used to it. I did grow to like Brian over the years. People are used to Brian and his sound. If it was a drummer or a bass player we were talking about, then yes you could replace them easily. Vocals, not so much. Not as many people would buy the albums.
As an example, could any other singer replace Robert Plant in Led Zeppelin? It ain't fancy either is it?
Yeah I thought they went and got a guy who did a pretty good rendition of Bon Scott at the time.
Which I found a bit off putting. But after a bit I didn't care because the songs were great.
I'm sure they could do the same thing again.
The really big loss is Malcolm.
He wrote the songs.
They could get 20 people to replace Brian but Malcolm is not replaceable.
He wrote all of the songs and music for Back In Black. Angus got some credit but I've heard that it was 99% Malcolm. That's not something you can replace.
From here in the best they can hope for is to be a cover band IMO.
Or to try to write songs in the style of Malcolm which will inevitably not be as good.