A designer bag for daily use

I have bought upscale bags and have gone through the decades with the popular bags of the time. I am now 68 and would like to invest in a nice bag to carry for maybe the next 20 years. I have zero interest in the Birkin Hermes line as that is so over the top with people trying to mimic celebrities, royalty, and current influences.

I also like a softer less constructed bag for every day. My mom had a birkin and taught school for a million years and used it as her school briefcase. It was rugged. My grand daughter, her great grand, took it when she started her first real job out of college. It is still a good looking bag.

I want a bag that is understated, functional, and wont go out of style in a hot minute. I look online and they all just start looking the same. Suggestions?