IMO how you get there is reasonably intuitive -- as with most sites that don't have a logout button on the main page, it's in the account/profile dropdown usually accessed by clicking on a photo or arrow in the upper right.

However I will grant you that once you open the triangle menu, it's kinda buried among all the other crap in the dropdown menu but it's in the lower left (right about "My Delta")

Is it that important though? On a computer you control it's not that important to logout, and I wouldn't login on a public computer anyway but if I were in a pinch and absolutely had to, I'd do it in an incognito window and then close it when done.