Other people have touched on this more eloquently, but I love that Ryland Grace is at his core a teacher. A middle school science teacher. Sure, his background as a former academic is also critical to the story, mostly because something about him needed to catch Stratt's eye and thus result in him getting dragged into the project, but more importantly than that, he hated being in academia. The book makes it fairly explicit that he wrote his controversial paper and insulted a leading scientist in his field because he was burnt out and hated the environment and got self-destructive as a result, which is a far less rosy view of academic science than I would have expected (and, frankly, completely believable).
And then he left and became a middle school science teacher. And that turned out to be his real calling. He was bright and creative and a little bit brilliant and a genuinely good scientist, and he gave that world up to teach kids and he loved it. Even after everything, after the Petrova Taskforce and Project Hail Mary and Tau Ceti and ultimately ending up on Erid, his calling is to teach kids.
As someone who has dipped in and out of the science communication/science education world myself, it's so important to me that Grace loves teaching, and especially that he loves teaching kids. People really devalue science communication work, and there's often this unspoken assumption that the people doing it just aren't "smart enough" to become real scientists, so they do scicomm instead. And everything about Grace flies in the face of that -- he's perfectly capable of doing the science, but it's not what he loves the most! What he loves and values and finds important is teaching, and I adore that. It's so refreshing to see, and such a genuine love letter to educators, and to everyone who chooses to prioritize communication and education regardless of how specialized they may or may not be in their field.
His happy ending is to be a teacher. And that's so important.