What needs to be kept in mind about the DD spinoff is that season 1 essentially had to be rewritten becuase Melissa McCarthy couldn't do it. So basically what we see in Season 2 was meant to be Season 1. So season 1 ends up just kinda being it's own seperate thing and any characters in it were not very likely to survive longterm. I thought season 1 was fantastic though.

If they were going to do a romance between them it would have happened WAAAAY back in Season 2 or 3 of the walking dead. There has honestly been no romantic chemistry between them and it would be odd to put them together this many years later. Daryl always just looks super uncomfortable any time Carol has tried to flirt with him.