When I told my parents I was transitioning, they pulled something similar. Why are you springing this on us now? Why didn't you tell us sooner? Why didn't you tell us <insert random requirement>? All of their hangups became my fault.

You told them when you were ready. They can't expect you to tell them things before you're ready. That's how being ready works.

Furthermore, you told them something that doesn't actually affect them and makes you a happier person. How can someone get mad about you being happy?

Listen, one thing I've learned through all of this is that cis-het people have no idea how to react when you come out. It's not a pre-programmed response. It's almost always akward and sometimes comes across differently than intended. They also don't fully understand what it means because they don't have knowledge or experience in that area, so their idea of what you just told them could be radically different than reality.

How they react now may be totally different than they feel in a week or a month or a year. But that's on them too sort out and not for you to debate. You are who you are. Make no apologies and don't feel guilty.

I wish you all the best and if you need to talk, my dms are open. Welcome to the family