Love Barcelona, go every year before Mallorca and I’ve never had any issues... though I tend to stay away from some of the overtly touristy areas. I’ve traveled there with tons of different bags and think it can come down to being aware.... though this can be difficult if you’re in the middle of a crowd. I’ve used my PM and an old Chanel boy cross body to name two.

If you’re really concerned about things like slashing (which is known to happen sometimes in BCN) and don’t want to have to worry at all, here’s a Travelon backpack I have that doesn’t look like a travel bag at all imho.