I have no problem with any of it. It’s a big galaxy. I bet others survived Order 66 as well. Everyone has their own stories.
This concept took me time to grow into, but I’ve since come to love the lack of strong (plot based) direct continuity/references. I was so used to the intimate story of the OT, that I lost sight of the fact that this is a galaxy wide story, and that these characters don’t HAVE TO pop up in other media to make the world feel whole. These characters all have their own paths, sometimes they cross, sometimes they don’t. But what the different SW mediums are so good at is staying true to telling their own stories, and letting us connect the dots on our own. Now, to me, that makes the GFFA feel much larger and more relatable to me.
None of my closest friends now have ever met any of my closest friends from college just 5 years ago, even though most of us live in the same area. Hera didn’t appear in RoTJ, but she was at the battle of Yavin. They’re just different stories.