Why couldn't Henry just embrace Mary?

It's complicated. Highly complicated. Henry resented the hell out of Katherine the longer she went without producing a living male heir. Had they been so blessed, Henry would have been much nicer to everyone, including Mary, and she would have been well-married. Intransigence taken to the 9th degree.

Remember, Henry thought his throne was far from secure, his father had won the last battle of the War of the Roses and still had to spend his reign putting down pretenders and uppity nobles. Henry knew damn well that neither his reign nor his succession were secure, some of the power brokers would try to put some puppet on the throne when he died instead of his designated heir, if there were any heir but a legitimate son raised to rule.

But really, he did treat Mary shabbily, even before the divorce. He should have raised and educated her as a potential ruler, and married her to someone who could co-rule or act as regent, but he seems to have thought so little of her he did neither. Nobody knows if that was because he was fixated on the idea of breeding a legit son, which he was, or if he just didn't think that Mary had the brains and charisma to rule. Probably both, and that was before she refused to go protestant or accept his marriage to Anne Boleyn. After that, his disdain knew no bounds.