OK, I'll weigh in on these mary janes, because I sampled them also. To me they are quite 90s, classic goth (I wouldn't say they're quite like character shoes, having worn that kind of thing in high school with miniskirts, haha. To me, those would be a lot lighter overall with a distinct heel and thin soles. But anyway ... !).
I ignore all warnings about being too old for anything. IMO it's all in how you wear it, like Vildy says. Anything can work, really, in the right combo. I say try them with whatever you're inspired to, and see if you like the look.
Mary janes in general are so classic and there are so many flavors of them. I sport a few different kinds and don't look at them as a class that I should adopt or not. For me it's about the individual pair and does it work in my wardrobe?
All that said, I've decided to return these because they are, well, plastic. I have a policy of preferring leather for anything closed-up. Sandals can slide on that sometimes. It's now customary for gothy 90s club styles to be plastic for a few reasons, and I'm not such a big fan. But that's me!
Aesthetically these are very nice-looking shoes, but I know that going forward, I personally would feel wrong about the lack of breathing and give, and plastic shoes tend to crack and scuff ... besides the environmental concerns. They are tempting, but I'm going to hold out for leather myself.