HK is one of the game that you're "supposed to like". Dude, it's a heckin SOULSLIKE METROIDVANIA with le charming hand drawn animation and heckin cute bugerino aesthetics [soyboy face]! Well apart from the visuals it doesn't really have to offer much else.
...but still pretty good, even though it's "merely" a competent (the most competent?) Earthbound/Mother "fangame". The soundtrack is AMAZING however, no doubt. One of the real drawbacks (subjective) is the excessive (compared to Earthbound) amount of self-aware "le randumb" humor (thankfully toned down for Deltarune). Thing is, the Japanese don't understand sarcasm and irony, so if you are Japanese and see a man that has turned himself into a dungeon (or a pickle), you're supposed to find the idea "serious" funny in a manner one laughs at normal sitcoms (or not), instead of ridiculous in a post-meta-ironic way. Or maybe you should be admiring his... determination?