Reddit reviews Brahms: A German Requiem

Most answers so far recommend other Baroque composers because of how you phrased your question. If you don't like the "lazily chaotic" character of other music, we're thinking you might prefer more complex, polyphonic musical forms. That's where you get the elaborate contrapuntal music such as fugues that bear lots of repeated listening and hold up well to so many different performance approaches.

Let me answer in a different way, focusing on the "shallow" part. Bach has a certain depth of sincerity and religious feeling that is not achieved by any other composer. I do think you get lots of later composers who manage to achieve profundity although it's admittedly of a different character. Brahms comes to mind- Ein Deutsches Requiem is gorgeous and formally rich, even including an extended fugue with explicit homage to Bach. Mozart, flibbertigibbet par excellence, has a fantastic Requiem that is totally unlike most of his other music and which no one could accuse of being shallow. There's really a lot of music in this vein.

TL;DR- I answered the question with music recommendations because posting "Beethoven" as a one-word answer would make me feel lame.