“do not have places that attract tourists”
That is a big exception to your other good points. They get mobs of muslim tourists for Mecca and Medina.
They include increased tourism in their 2030 vision, but as you rightly point out, they have a long way to go to develop a diversified economy.
And they have a short time to get there. Oil is unlikely to get expensive for any sustained length of time, with the US pumping, shale oil plentiful, and solar developing quickly.
One prospect is that they could invest in the near abroad, like agriculture in Iraq, and low-cost manufacturing in Yemen, as part of their diversification.
I thought about Mecca and Medina. The haj visitors are already part of their economy, but they need to expand their economic base. I agree those cities would be big draws particularly in the years after opening them up, but that allure would fade quickly. Their best bet might be becoming a major financial center like Dubai, HK, and Singapore.