> They are slow because Windows got heavier while the hardware stayed the same.

That is not true. They are slow, because ALL software got better and more advanced and that is not only the operating system. It always makes me mad when people say that macOS is so optimized you can do more than on windows.

No. Old hardware not having a hardware decoder for modern youtube videos won't play them.

Modern webpages full of interactive realtime features won't fit in the RAM or will be bottlecked by a cpu. Yes, the modern linux will run, but are you going to do anything more than opening a notepad or old software? No. You are not going to use modern web apps or software on it.

Is it okay? Yes. Optimizing for old hardware is EXPENSIVE. Just move on.