I like how things turned out, and while I agree the Goddess isn't without fault in this situation I don't believe she deserves as much hate as she's getting. My guess is she doesn't like to directly meddle in mortal realms too much otherwise she could potentially cause unnecessary havoc(or simply because she doesn't want nor should she need to babysit a species that
should be fully capable of taking care of itself). Not to mention that the whole Demon King scenario was brought about by humans themselves and thus was the responsibility of said humans. The fact that she even brought someone from another world to help was her going out of her way to help those selfish, disgusting children that brought about that hell all on their own. Not only that, but those humans didn't even learn from their previous mistake that created the first demon king and killed the angel sent down by the goddess herself. If I was in her shoes I'd have been fed up with their nonsense and let them perish before starting over, but the fact that she still wanted the world to be saved is extremely generous on her part. As for why Jun suffered as much as she did in her reincarnations I agree with the Karma bit, but I also think the Goddess should have helped Jun out more considering the Goddess was responsible for bringing Jun to that world to begin with.
Regardless, the Goddess isn't without fault but nor was anyone else. Jun definitely should have taken a more proactive stance and gone with Marcus to slay the Demon King since that was the whole reason she was brought there(of course she didn't know what was going to happen when she stayed behind, nor did the Goddess apparently. Jun didn't deserve her fate.), but the shitty king and nobles that had Jun killed are the most at fault. Thankfully things ended well. Jun and Marcus are reunited along with all of her reincarnations and their respective heroes, the current nation is being led by royalty that seem to actually be decent people for a change, the faith is on the road to becoming less corrupted and thus a better guiding light, and the Goddess didn't lose the rest her precious(albeit fucking stupid) children nor the world they live on.
Edit: Also, just because she's a Goddess doesn't mean she's perfect. Close to it, sure, but I believe Gods and Goddesses are just as easily capable of making mistakes or not doing things as efficiently as they could as humans or any other sapient creature. Just depends on the individual entity's experiences.
@ThatOneJester Honestly, they deserved their fate. From what I understand their souls were indeed freed(unless the plural "souls" mentioned before was referring to the multiple heroes rather than the scumbag nobles, in which case disregard this) so they likely aren't still alive as some sort of monstrous form. However, I highly doubt they went to some heaven equivalent afterwards.