While it was sad to see Paige at her lowest ebb in season 5, Young Sheldon season 6 should not bring back the guest star to avoid reopening a Big Bang Theory plot hole. 

It is a shame that Young Sheldon's Paige plot hole renders the spinoff unable to bring back the character, as Sheldon's earliest rival gives the show's star a rare character to play off who is at least his intellectual equal.  Often, Sheldon is unfairly matched as he faces off against peers who are less intelligent than him or co-workers who are as smart as him but boast vastly more life experience and social graces than Young Sheldon's guileless lead.

This made Paige a welcome person when the character occasionally appeared on Young Sheldon since she was the show's only character who experienced the same social struggles and academic acumen as the eponymous hero.

However, this is not enough reason to bring the character back. Young Sheldon closed the Paige plot hole perfectly when the series clarified that the character abandoned academia and, as such, had no reason to cross Sheldon's path again. Not only that, but their thwarted rivalry/quasi-friendship never resulted in anything consistently beneficial for the duo, so it would be understandable for The Big Bang Theory's hero to not mention an acquaintance who left his life at such a formative age.