How are you planning to fix a ripped t-shirt without making it look terrible? This era, we are wearing very simple clothing which is disposable, also very durable (jeans). I mostly wear shirts/tshirt and jeans. I don't even remember needing to fix any and still have my old jeans for over 15 years.
I don't wear t-shirts often, and don't think any of mine have needed mending. I do wear thin long-sleeved sweaters, so if you don't mind I'll answer for those: The most common problem starts with a small hole somewhere, frequently just next to a seam, and is mended in a minute or two if caught early. Disastrous tears are a different matter, but happily also a rare one.
