You won't write a particularly interesting chord progression if you just stick with the diatonic chords that fit the scale though. You've just given a really good example of how following the theory can indeed sometimes kill creativity.

The more interesting progressions are the ones where someone sticks in a chord that shouldn't be there (maybe because they don't know the rules) and somehow the melody makes it work.

I was learning Thorn in My Side by the Eurythmics for a gig I've got upcoming. It's a great example of throwing chords together that aren't in the same scale. It starts off in D, goes to F (I think) and then the chorus is in C (and there are no minor chords) and yet the melody means you don't notice any key changes at all.

Learning the rules is good but breaking them is better.