I'm usually live in dungarees and DMs it's only today I put jeans on, I got them from a charity shop and made the rips.. trying my £3 bargain out.
I'd say whoever said it is jealous. For a start you're slim which a lot of people aspire to but struggle to achieve. You're experimenting which lots of people don't have the guts to do. You've got tattoos and don't feel the need to cover them up to appease people who don't like tattoos. You're wearing a simple, basic outfit and look good in it. I find people can be very jealous of a confident person, which is what you look like. That comment about dressing your age was designed to put you down, diminish you, make you uncertain and less confident.
I don't know if I dress my age. That depends what you mean by it. Do I dress like a current 20-something? No. Do I still wear the clothes from my youth mixed with modern pieces? Yes. Do I wear items of clothing sometimes seen as the preserve of the young, like sleeveless top, mini skirt, latest style jeans etc? Yes.
A lot of the time I think "dress your age" means jealousy. It's code for "how dare you be so confident as to be able to wear whatever you like, and why haven't you got fat yet?" as if with both you've committed some sort of crime. I think some people want anyone past the first flush of youth to mark themselves as older by wearing the most basic of generic clothes, that may not fit well or be in good condition, or else look very obviously dressed up in a try-hard, young-people-would-never-dress-in-this-style kind of way. Like the clothes are the equivalent of a tattoo across you face reading I'm Unfashionable And No Longer Young. And if you don't conform, you're fair game for snarky comments about dressing your age.