Perhaps here's a way to look at it: Without Creative, you have to research Mysticism quite early, when it takes 6 or 7 turns that you'd rather spend adding worker-techs, Writing, or whatever. With Creative, you'll eventually have to pick it up, but probably at a cost of just 1 or 2 turns, so being Creative sets your research ahead by about 5 turns.
Likewise without Creative, you have to build a monument in each of your initial cities except the capital. You could work a plains-forest-hill for 7.5 turns to build it; or work a 3F tile for 8 turns and then whip it (with some overflow); or more likely, chop a 20 hammer forest and come up with 10 hammers somewhere -- ~2.5 turns of productive output, plus 4 worker-turns, plus a forest that can't be spent on something else. And in all these cases, your wait for access to your second-ring tiles will be 5 turns longer. So total output lost is probably less than 5 turns for those cities whose best food/production tiles are in the inner ring, but more than 5 turns for those with the best tiles in the outer ring. (Alternatively, you can build Stonehenge. That generally takes more than 5 turns worth of production, but also returns GPPs. Call it a wash)
So very roughly speaking, Creative saves you ~5 turns in the early game. Does that sound about right? Would you be willing to pass the first five turns before settling, in exchange for the free 2/turn culture?
Then, is that enough to make it a good trait? Spiritual almost certainly saves more turns of anarchy, but it does it spread throughout the game, and earlier is better....
peace,
lilnev