Welcome to the forum!

Are you talking about the default for new, empty documents?

This is a matter of the template used for new documents.

Or are you talking about already existing documents - with music in them?

This is a more complicated matter - since there are many different items:

- chord symbols

- clefs, time signatures, accidentals, noteheads, flags

- expressions

- articulations

The old Jazz font is not owned by MM and is licensed to them. It has fewer characters and will never be improved beyond compatibility fixes. If you like it, great but… There's a reason why the Broadway families exist.

Otherwise, we need more information per Peter's questions.

There are a number of third party handwritten fonts on the market, also.