To make a song better, a few simple changes can make all the difference. Five ways to make rock songs better are:
I. Simplify chord progressions
Make songs better by taking progressions of six+ chords and boiling them down to their main parts. "Stairway to Heaven" may sound complex, but it's really only five chords. Bands like the Ramones and Green Day have made an art of the three- and four-chord pop single, so we know success doesn't depend on complexity.
Complex structures make players work harder, and music fans don't necessarily respond any better than if the song had a simpler structure. Try taking some chords out of one of your math-ier favorites and see if it really makes a difference. It's usually possible to keep the same mood without going through so many steps.
II. Make songs better by making songs shorter
Amateur rock bands might struggle with song length more than any other genre's musicians do. Causes include (but are not limited to) showing off, slipping into "jam mode," and writing hypnotic refrains that don't successfully hypnotize listeners.
Too-short songs may leave listeners unsatisfied, but too-long songs bore them. And what's wrong with leaving your fans wanting more, anyhow? If it's really too short, tack on another verse or whatever. Just don't make songs too long. That's death, and pretty much everyone does it.
III. Make songs better by playing with tempo
Make a song better by slowing them down or speeding them up. Most songwriters pick tempos for their music by accident without thinking how tempo affects it at all. This is silly.
If you meant your song to go at breakneck speed, go ahead and experiment by playing it slowly. Often the best slow chuggers originally came out as ripping fireballs. Sometimes quiet, little ballads like "Brown-Eyed Girl" sound fantastic with a one-two beat. You never know until you try.
And speaking of not knowing...
IV. Let your band mates change your songs
Make songs better by asking your band members to make them better. They have creativity, and they have ideas. Every song will be better if everyone feels welcome to add their perspective to the material.
Lots of bands have a tendency to let each member's songs stand as-is. If that works, it's pure chance, and probably they'd benefit from some revision.
Don't just keep an open mind, actively ask the drummer what he or she thinks — the bassist, the rhythm guitarist, the accordionist, and the mook playing triangle, too. That's how to make songs better.
V. Add texture by letting instruments rest
Make a song better by letting just one or two instruments carry it occasionally.
Jazz figured out a long time ago that it's obnoxious to have 100% of the crew playing 100% of the music 100% of the time. Rock bands often have a hard time with this.
It's ridiculously easy to let everyone drop out but the bass player for a few measures. Or the drummer. Or the singer. Or whomever. The point is that your band doesn't need to have all the lights on when the song's fun lies in just a couple rooms. Let the others come in when they're needed.
And if they're not needed? Let them take five! The modern motif of "nobody gets to rest until after the set" is bizarre. Audiences respond very well to changes in band size during a set. Use that.