very true but Cher had a number 1 single in her early 50s. But you could argue that Believe was an exceptional track. Or that compared to the 90s our culture is even more ageist and that a woman in her 50s couldn't now achieve what Cher managed in 1998.
Back then though it wasn't just teens buying singles, you had the parents & grand parents since it was Cher, also it was the first song to use full auto tune & to feature no instruments, it was gound breaking at the time
Also why Madonna gets low sales now is not that it's down to shims but the fact that people are just sick of her, she was the biggest star in the music scene in the 80s following MJ then throughout the 90s & 00s making over hyped comebacks, 98, 00, 02, 05, 08, 10 and bloody 12 which flopped here
People are just sick of her coming back tbh ffs, Cher is really just too dated, Womans World could of been a hit here if she performed that as opposed to that other song which was too dated for Radio play on R1, Capital and hell even Heart
Kylie however I can still see her being appealing to the teens as she is a MILF and is capable of releasing something modern and it doing well, her on a typical Calvin Harris track would do well & Jay Z is writting her new album who I believe makes Rihanna's albums?
Kylie isn't fully dated yet she is still marketable if you get the right sound just like Britney who scored a no1 in early 2012 with will.i.am and a recent top 10 hit here with Work Bitch, which would of git a top 3 spot if was promoted here (she didn't perform the song here which impacted he chart placement, if on X a Factor it would of got to no1 prob.)