General songwriting tips? How to write something great?

I agree with Richard. While having a band definitely does help, we should keep in mind that there were amazing composers that wrote entire operas by themselves. People like Wolfgang Amadeus Mozart and Richard Wagner wrote the lyrics, the melodies, AND the parts for over 10 different instruments, all with their own ‘chair section’ (1st chair clarinets took the leads while the 2nd chairs usually played more basic parts). So it’s not entirely impossible to do these great, complicated things on your own. But it all stems from one idea, whether it be a chord progression, melody played on piano (or guitar), or even just a sense of emotion you want to convey. For example with this, Hans Zimmer wrote the music for the stampede scene in the Lion King movie. He utilized what the characters were expressing and the atmosphere of the scene to write his music.
But it all starts with something simple. You build over the first step and you keep building on ideas. Spend time thinking to yourself, “This is MY song. If I did have a drummer, what would I like them to play underneath it?” It’s honestly something you just have to sit down, focus on, and really start creating your own ideas. I like recording my ideas to a metronome on my phone’s audio recorder and then playing over it. Or sometimes playing along to drumming backing tracks that will also open up ideas for rhythm tracks.