Could a jazz singer make it big in today's music market or do u have too be pop?

What do you mean by "make it big"? No one can predict whether you will "make it big" regardless of what genre you choose.

I think Cecile McLorin Salvant is doing OK. If you listen to her, you will became a total fan.

https://www.youtube.com/watch?v=NkmGue2WQyg

Amy Winehouse was seriously influenced by jazz singers . . . It always a big mistake to simply go for the $. If you love Pop go for the Pop . . . but otherwise: https://www.youtube.com/watch?v=j49m1DUYUy8

Define "make it big".

Jazz singers can make a good living, but they can't pack stadiums. (But is a stadium really a worthy venue for jazz?)

IF you consider Norah Jones to be a Jazz Singer then yes.

Jazz is an acquired taste enjoyed by a small percentage of people. The mass market has always been pop music. If youre really really REALLY good looking then maybe you have a chance.

There are some jazz singers that make the money and can pack a venue,,, Michael Buble and Diana Krall come to mind,,, but they are few and far between,, jazz is becoming a niche market, not many of us jazz fans left.