I think the term is like all such terms situational and fluid. The mean of dress also varies considerably from urban to rural and regionally.
I see older women wear very bold colors. Maybe not fishnets, but leggings, tights etc. I think sometimes an older transgender woman could be stereotyped for wearing certain styles more than a CIS woman of the same age, but both will attract attention with a bold style. To me fishnets sort of say - rockin new years eve party, or club wear but i do think they are great.
I too buy a fair amount of clothes from Target but i also get stuff from H&M which i think has an even younger vibe. Still, i would describe my style as "soccer mom". I wear jeans and wedges, jeans and sandals, jeans and boots in the summer. My tops are usually lands end, LL bean, or maybe on the "wild" side, some peasant top. When i wear skirts or dresses my legs are bare in the summer or in tights in the winter. I see women from 20s to 70s in my style.
I always strove to be "age appropriate" despite its ambiguousness, mainly because i was scared about reinforcing stereotypes of trans women but i think or worry about that less now. I just ended up liking the style that i chose. Like all style though it continues to be refined.