I think there's a pretty big difference. Hobo implies worthless, "washed-up" as you said. Simon doesn't seem that way to me at all.
We know he never wanted to/enjoyed leading humanity. The fight against the Antispirals was over, so there were no other giant space battles to pursue. Presumably he would have liked to live a relatively quiet, happy life with Nia, but she's gone as well.
So what does he do? He travels the world, living as he wants without a ton of paperwork and bureaucracy. If there are wrongs, he rights them; if there are problems, he solves them. It's not a grand, superfabulous life, but Simon never wanted that anyway; instead of being bogged-down by the realities of being a hero, he fades into history, a legend in his own time. It seems a fitting end for him.
Besides, with his kind of spiral power, that by no means could be The End, just a gap before his next adventure.