D.N. Angel is underrated.
Its plot and characters may seem simple, but its execution is definitely noteworthy. The main and side characters are charming and believable, the story's magic system is compelling, and I adore the characters' overall relationships. Daisuke and Dark are a great pair, and while the former may seem like a typical protagonist he's a nice guy and I want him to succeed. His interactions with the cast have good chemistry, particularly with Dark and Hiwatari and the "romantic" bits are reasonable for the characters' age group.
That being said, D.N. isn't perfect. Its story strays a bit from the manga so some details may be lost in translation, especially with the ending. While I am fine with the cast, some may find them as one-note or annoying. The artwork is definitely as old and retro as the early 2000s, and the ending can be seen as unsatisfying. Regardless, the good outweighs them.