Earlier quoted context omitted.
Probably depends a lot on what you are buying. I've been buying electronic components, Arduino compatible boards and sensors, that kind of stuff for a while. Quality has been pretty solid with all of it, about 100 orders so far across a bunch of different merchants. I've heard that clothing can be really hit and miss.
Yes, clothing is problematic. Quality isn't great, and you need to order at least 2-3 sizes up. Even then, the sleeves might still be short: XXXL just means you're getting the overweight size, not the long-limbed size.
Same is true in the US though: American L translates to XL on shirts and XXL on boxers and the like in my country.