Look at any primitive group of people living anywhere on planet earth; and they will probably have T-shirts, but if they don't happen have T-shirts, then they probably will steel tools of some sort. I don't mean iron tools- I mean steel. They CAN'T make steel- there is no way they could make steel.
Humans have lived for tens of thousands of years without any steel, so human can survive without steel, but you won't find any group of people in the world today who haven't had a steel item of some kind.

Decades ago, it was big news that a group of humans was found that had no contact with the modern world. Frankly, I doubt it was completely accurate- I would accept, that they had little contact and the contact they had was indirect. But even if it was true, that was something considered as very rare- headline news. And it very unlikely to have any such group today [btw, it would again be big news].

Here is another thing to consider, you won't hear about some group of hippies who wanted to escape from the modern world and have been living in the wilderness somewhere for forty years without *any* contact to modern world.
It won't happen. Someone could lie about it, but it won't happen.

And as being stuck on some desert island for decades- it isn't going to happen either- it's a pure fantasy.
Anyone could choose to completely disappear and not be in contact with human society for as long as they wanted. But no one does this- unless they *have to do it* and they can only manage do it for a short period of time.