I really wanted to see who they all ended up with

They’d have probably only survived a few more years after the battle before they died because most of them had manifested those marks so it’s probably better we saw a happy ending with their descendants instead of watching them die young

I think it was kinda obvious, especially with the last chapter: Tanjiro with Kanako, Zenitsu with Netsuko and Inosuke with the pigtails butterfly girl
Im guessing the surviving pillars didn't get married (except Tengen ofc)

There's a possibility that giyuu and sanemi are married, that boy named giichi or that policeman are probably giyuu or sanemi's descendant