#1. Shouldn't return at the Royal Rumble: Goldberg
It doesn't take much to realize why Goldberg shouldn't return at the Royal Rumble 2021. While WrestleMania 33 in 2017 seemed to be a fitting end to his career, he decided to come back and had a disastrous match with The Undertaker in 2019.
He squashed Dolph Ziggler and would return in early 2020 to challenge 'The Fiend' Bray Wyatt for the Universal Championship. He won the title in what was a controversial move.
While he was supposed to drop the title to Roman Reigns at WrestleMania 36, Braun Strowman took that spot instead. Goldberg will add no actual value to the Royal Rumble match, especially without a crowd. He is unlikely to be a surprise entrant, but WWE seems to love bringing legends like him back for matches such as the Royal Rumble.
However, the Royal Rumble match could do without him. He would add some star power, but even his 2017 Royal Rumble appearance was brief (albeit, impactful). Goldberg is better off on the sidelines.