The world is noticeably empty due to hardware limitations.

The style is entirely informed by hardware limitations. They did their best with what they could.

Tears of the Kingdom is a Switch exclusive.

The style is influenced by Breath of the Wild, but nothing about the development of Tears was held back by the Wii U.

Lack of ram meant it could only handle a couple trees at a time

That's not true. There's a couple of forests that are as dense as gameplay can reasonably allow.

Most of the environments are empty planes with a 1-2 trees I think they needed to use a lot of tricks to have more than that. It might have also been an ai pathing issue

Most of the time isn't the limitation? Maximum is the limitation. Look at the forest on the plateau. Look at where memory 11 is in BotW. Look at the lost woods.

Sure, most of the time there are just a few trees, but when they want to they blow right past that