A Galaxy Next Door is best described as average. The premise comes off as uniquely unoriginal, with the method for the two main characters being tied together putting forth the only amount of individuality this show has. Every other aspect of the show ends up becoming a trope galore. The show struggles to ever have a definitive identity, constantly teetering on the line of breaking out onto it's own but never committing.
One of my largest gripes is how the show is almost too happy. It's so cornily happy without any irony it can begin to be overwhelming at times. The first few instances come off a sweet and nice, but after watching further it begins to weigh down on the enjoyment of the show.
The main character is one of the most boring imaginable. He's the typical "nice guy" character in anime, which isn't inherently bad, but he possesses no individually to his character. If I were to go to another anime and grab a different "nice guy," any person would struggle to tell them apart. His design is especially disappointing as a show with such nice visuals at times produced one of the most bland main characters. It's understandable that he wouldn't be some absolutely crazy design but he feels as though you took every romance protagonist and averaged them into a design.
One of the few positives is that it has themes of child-care, which while not to my tastes, very well may be others adding some level on uniqueness to the show.
I can't say the show is terrible as it's not an awful watch, but I can confidently say that I don't recommend it either. There's a lot more better romance shows out there that would be watched before you get to this one, but if you're really strapped for romance, it's not the worst option.