Don’t replace your brass. It is an alloy of copper and zinc. It has antimicrobial properties.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5551251/

That might be useful in a world where people are concerned about COVID.

Oh come ON. We're going to accommodate Covid in hardware selections?

This, if I had to guess at the "age level" is corroded, junk, green tinged cheap brass the OP is referring to..

In answer to the question? You can have any finish you want in the interior. Buy a quality handle, change hinges as well. See Emtek.com for a wide selection.

Really and I bet probably not solid brass anyway. Get what you love and if you are worried clean all the time just like the rest of us.

There are no rules and not everyone can change an entire house, as costs add up very quickly. Our curved brass handles and hinges were recently replaced with modern black ones on all interior doors. We left the 5 exteriors doors as is, as it would have been too expensive and no one notices except me. It was worth updating and more impactful than I thought.