No argument about AC/DC not really changing anything up in their song writing and playing over most of their catalog, but I will push back on a couple fronts.
Yes most radio/single releases sound a lot a like, but on album to album basis, I beg to differ on that sentiment. Each album has its own vibe or aura/theme about it that makes each one kinda unique, even in the Brian Johnson years and each album has its own gem that most people dont hear because they just listen to whats on the radio, rather than giving an albums a front to back listen. Ballbreaker as an album has a different tone and feel from Razor's Edge. Razor's Edge has a different vibe from most of their 80's albums. Stiff Upper Lip has a much more jazzy feel/vibe to it than almost anything else they did.
And on them not changing much or "progressing", while yes its fun to go on a journey with a lot of bands as they grow over the years (especially metal bands), its also nice to have a band that you know what you will get, and its going to kick ass. Some bands will progress, and some take you on a fantastic journey over the years, others.........not so much.
@Drivesaitl Its not AC/DC's fault rock got stagnant. They were a revolution for their time because they stayed true to their form and brought a brand of hard rock that nobody else did. Its why they've been able to endure over the decades while so many fads have come on gone over the time. They didn't sell out to what the "popular" crowd was into by hitching onto anything they never really identified with before. I think thats why they've managed to gain and maintain the following they've gain over the almost 50years they've been around. AC/DC knows who they are, what they're good at, and full on embrace it regardless of what record labels might think, or what the fad of the day is or what their nay sayers say. And to wrap things up, IMO thats what makes them so easy to relate with and for someone like me to be such a big fan. They're a no nonsense blue-collar hard rock band that goes balls out making fun riffs that are fun to listen to, fun to learn to play, and fun to just flat out rock out too. If modern day bands don't know or dont figure out how to tap into that themselves.......that's not AC/DC's fault.