The view of t-shirts as being underwear and vulgar for outer wear is definitely rooted in a subjective preference for an era rather than a true aspect of the Faith or Catholic tradition.
No, it's rooted in the design and use of t-shirts. They are designed to be utilitarian, informal, unisex. Catholic common sense needs to be applied, and while different times have different ideas of fashion, there is no doubt that t-shirts are slack.
Yes there is a doubt. You aren't very good at being objective, or rising above the culture you grew up in.
A T-shirt is just a piece of cotton fabric sewn to cover one's upper torso. When properly sized, they happen to conceal the various "details" of anatomy, so they certainly pass Catholic muster when it comes to morality, modesty, and decency.
If you can still see that a
woman is wearing that shirt (as opposed to a man), GUESS WHAT? All women on earth aren't going to go out tomorrow and get double-mastectomies just so you can stop being tempted.
You're telling me that a buxom woman in a
dress has no visible "bumps"? Give me a break.
If a woman is wearing proper...ahem...garments... and wearing a loose-fitting T-shirt, there's nothing that can be more concealing except maybe a burqa. I'm actually serious, not facetious.
If you still can't stop thinking about what's under that pile of clothes, again, I feel sorry for you, and I pray you find a spouse so your temptations can end. It has to be rough being 36, unmarried, and WANTING to be married for years on end.