Michael Burnham being Spock's sister
Talk about shoe-horning concepts that didn't need to be there. None of the captains brought into the show had ever been connected to a prior major character before. Jean-Luc Picard wasn't James Kirk's great-great-grandson. Benjamin Sisko had no prior ties to captains, other than being affected by Picard's time with the Borg.
But even then Sisko wasn't Picard's crew member, he was a victim of a battle and barely knew Picard. Kathryne Janeway wasn't a student of Picard or a relative of Kirk, and Jonathan Archer had no prior attachments to anyone, mostly because they didn't exist when he came about.
Trying to shoehorn Michael Burnham into Spock's family was done solely to bring Spock into Discovery so they could market some nostalgia alongside the show. It didn't work for a variety of reasons. Mostly, it retconned Spock's entire life needlessly.
They tried to force in a new relationship between the two and it didn't land with the audience. But what was worse was that they tried to show off how "good" and "cool" Burnham was in the relationship with Spock. This really made the character feel lost and unoriginal. They tried to have her be a better version of Spcok, and fans rejected it. It was the wrong move.
Also, what a terrible name for a grand character concept.