For me it's his childlike wonder. Things I've grown to take for granted, he's seeing with fresh eyes, and he really appreciates it. Thanks to him I bought a copy for PC and started a new career. Enough has changed since I started on PS4 that it feels fresh to me. It doesn't replace ED directly (they really are two different games), but it's now competing with X4 and Space Engineers for my limited recreation time. ED, on the other hand, hasn't been properly played by me for months now.
ps - I'm spending all this money on other games (including one I already owned on PS4), and yet I refuse to give Frontier money for Odyssey, even free gift money! That's a statement in its own right.