Xenoblade has no relevance to anything that came before it (aside from a small couple of references).

Xenoblade 1, 2, 3 can be played in any order. They are self contained aside from certain references. 1 is more serious, 2 vastly more light-hearted (for most of it, anyway). 3 takes place countless centuries after the other two with references to them in certain circumstances, removes the anime-ness of 2 and makes things vastly more serious. There's really nothing lost playing them out of order.

Playing in order gives you the "oh shit, it's that place", or person or music or whatever experience as you go on, but you would get that just as easily in any order I'd imagine. And the game works great on Yuzu on PC in 4k too.

Edit: yes there is an overarching plot in the trilogy, which reaches its conclusion in 3's expansion. But the games are structured in a way that is best for new players while rewarding long term fans.