She is OK. She is gorgeous and a lovely lass too.
As a singer? Not brilliant. Just good.
Same as many others....... Madonna, Taylor Swift, Rihanna, Britney Spears, Spice girls, Girls aloud, Bananarama, Kim Wilde, Toyah Wilcox, Hazel O'Connor, and a multitude of other singers...... And they are almost all COLOSSALLY successful. Not the best singers, but hugely successful and popular.
Sometimes it's not always about having the best singing voice; it's about the act as a whole, the stage presence, the image, the looks, the music, and the songs.......
Kylie has done pretty OK for 30 years now. She must be doing something right!