Not every chord has to be all that complex. I changed one from a 7th to just a minor triad, and it is fine. I don't have to omit the fifth from every chord: sometimes the chord needs that note to sound fuller. These things took a while for me to discover, because my default chords are always the 1st, 3rd, and 7th. That works fine, but not for every single chord. I was a bit afraid of sounding simplistic, but my real temptation is to go overboard on chord extensions.
I also discovered I could use a maj 7 in place of a dominant 7. The dominant seven tastes slightly tart and tangy to me, whereas the maj 7 is a bit ethereal.
The minor is not "sad." Especially the minor chord based on step III of the scale of the key you are in. This chord to me feels triumphant, as a substitute for the tonic.
Use the notes of the scale, but in an unusual sequence. The melody has to either go up or down, or up or down in arpeggios. There are only 12 notes to work with, and seven in any given scale, so you'd think all the melodies would be taken by now.
My favorite melodies are probably "Monk's Mood" and "I'll Remember April," plus a few by Bach. Bemsha Swing is up there too. And Lullaby of Birdland. For me, melody is the equalizer. By this I mean that a melody is as good as it sounds, irrespective of its authorship or provenance, or how easy or hard it was to write.
There's a composer/pianist I really like a lot, Andrew Hill. I have a lot of his Blue Note albums. They have a good texture for listening to while working. But I don't find that he has a talent for melody per se. I've never had an ear worm for one of his songs. A lot of music is very nice, but doesn't have that melodic quality to worm its way into your brain and make you want to listen to it forever.