do the gedolinm get to say about things not directly related to halcha but more of how one personally lives their life…even if it is not written in the torah or gemara?
Teen, there is a big difference between halacha, advice and societal norms.
The rabbonim 100% get to decide halacha. Then it is your choice to follow or not (preferably follow).
Advice is offered and its your choice to follow it or not. I have never heard a Rabbi say jeans are assur. They may frown upon them though as a garment that should be avoided.
Societal norms are what people do. Generally, they follow halacha but dont necessarily have any halachic basis to them. Sort of like yeshivish men wearing black and white – its what they do. Is there anything wrong with a colored shirt? No, but yeshivish men dont wear them usually. Its your choice to follow societal norms or not, remembering that people may look at you funny if you don’t adapt to the surroundings.