Agreed. A number of us had discussed this up thread. There are some possible scenarios where it's not as cringeworthy as it first sounds. Perhaps Leland ran an operation that went south and a byproduct was that some people, including her parents, were killed rather than them being the direct targets. Even that is still very small universe.
I didn't have problems with her other connections, but this was one too far I thought!
To be honest - I don't think it's each individual case. It's the sum of them.
Like, if we had another character that has a tragic, unexplained past, and then we have an evil superspy on the show - I really wouldn't mind if they were connected. I think the original sin is connecting her this close to the franchises most popular character - Spock's adopted sister - in such a forced way. And once you put a spotlight on this trope - every single instance is going to be looked at critical, and if they continue to pile up at this rate, it's going to be laughable soon.
I really wish Leeland would have had this connection to another character - say, Stamets or Pike's past (in fact - him being responsible for something bad in Pike's past would actually make perfectly sense, them already having a backstory together).
I really think "Burnham as the main character of the show" should be more executed as "her doing the most important stuff every episode". Like early TNG-Riker was always the one doing the action, beaming down and stuff. And NOT "Burnham habving a personal backstory with every character and event in the show". That's okay for a few, limited instances. But every single one multiplies the weight on suspension of disbelief - it becomes harder and harder to take her backstory serious - and that's really not a burden you should put on your friggin' main character.