The leather versions of the Gucci Jackie 1961 and Prada Cleo are very classic and fit your needs (shoulder bag and good capacity). Both are open top bags though, so I'd be concerned items could fall out.
I think a timeless bag is one that matches the outfits you wear the most, and is practical for your lifestyle. For me, it's the Loewe Small Puzzle and Celine Classic Box Bag
I think a timeless bag is one that matches the outfits you wear the most, and is practical for your lifestyle. For me, it's the Loewe Small Puzzle and Celine Classic Box Bag