I think you’re getting confused between dye sub and HTV (heat transfer vinyl).
Dye sub is great, but as you said, very limited in that they need to have at the very least 50-70% polyester content, even then, the print will only stay on the 50-70% that is polyester.
Pro - breathable, lasting, great gamut, no weeding time. Great for intricate designs.
Cons - limited to polyester, pretty much exclusive to white tshirts unless you want to get a wide format.
Then there’s heat transfer vinyl, sticks to cotton and polyester but isn’t as breathable, especially on larger prints.
Pro - suitable for most textiles. Loads of different finishes (holographic, metallic, glitter etc)
Cons - usually a larger cost for machine, mostly wide format solvents are used. Not as breathable. And the big one, weeding! This makes the designs a bit more limited.
Naturally those two are the ones that most people get into initially but there’s plenty other ways you could go, screen printing, direct to garment etc. Naturally those have their drawbacks too, I don’t think I’ve ever seen anyone have good things to say about DTG, and screen printing isn’t suitable for short runs but the cost is a lot less for large runs.