Please tell me your intuition: Does this sentence sound clear and natural in your ears? Yes or No

Using synecdoche, a part for a whole," hearts" used in place of" men ", makes your sentence more poetic. It is understandable, but unnatural if we think of ordinary, everyday prose.
Nowadays men are no longer brave; they are greedy. This is clearer, less elevated in tone. Which is better is a matter of personal taste and context.

I would say this sounds more natural...

Nowadays, Peoples hearts are not brave anymore, but greedy...

Thank you both.