for Christina yes, absolutely. she would've been right at home if she debuted in the late 80s/early 90s much like other vocal prodigies of that time.
Should've known based on who quoted you . Madonna would've been just fine in the 2010s. In fact, I think a good number of legendary acts from the 80s would've had very successful careers in the 2000s
I think Austin would have been more successful if he debuted before Justin as too many people comapred them and I think that hurt his success in his career, living in JB's shadow