I think you're applying what Singer successfully intended to do in X-Men to Watchmen, and blaming Snyder for not doing what he hasn't done and never intended to do.
I mean, Watchmen is a mystery and X-Men isn't. For Watchmen, not having much of a connection to The Comedian doesn't matter because you are supposed to learn about him later. And through that, you connect with the character, as well as learn about the characters the mystery effects. It's supposed to make you wonder why The Comedian deserved being beaten up and killed. X-Men's opening scene was meant to garner sympathy.
It's simply not fair to criticise Snyder in this situation.