I would not call the Arab Revolt 'overrated'. It was important in many aspects. It was a blow to any attempts by the Ottoman side to picture the conflict as the struggle of Muslims as a whole against the imperialist Christians. It made logistics more difficult and diverted valuable resources from the frontline. Once you are not sure who the civilians behind the front support, it becomes much more difficult to plan an orderly retreat, something which the Ottoman Army never excelled at even under better conditions. Attacks on the Hejaz Railway by Arab rebels was also important in this regard. Moreover, rebels were also instrumental in keeping Ottoman garrisons under pressure and eventually taking over certain places away from the main frontlines, such as Mecca. The Revolt had an impact on the future of Turco-Arab relations too. It is an exaggeration to think of the Kemalists as simply refusing any engagement with Arabs due to their hatred of the latter. But it is nevertheless clear that the Arab Revolt did influence a large number of Turkish political and military leaders and intellectuals, who then saw it as a sort of 'backstabbing'. None of these were trivial.

But, did the Ottomans lose because of the Arab Revolt? That would be a stretch. The Ottoman defeat in Palestine stems more closely from two earlier attacks on Egypt (in 1915 and 1916), the Suez Canal, held at the time by the British. These attacks were led by Cemal Pasha (who later hanged a number of leading Arabic intellectuals and political leaders who were accused of conspiring against the Ottoman Empire with the help of the French) and the German officials (like von Kressenstein) and motivated in part by a German desire to harm the British in such a strategic location. These operations cost Ottomans dearly. When the British forces began their offensive, some forces the Ottomans could use in the defensive were already out of the picture due to the earlier attacks on Egypt. Moreover, as far as I know, the main striking force of the British Army in Palestine was formed by the good old Brits and other forces from the 'dominions', especially the Anzacs.

We also need to keep an eye on the greater context. Even if the Ottomans were to stop the British in Palestine and Iraq (which they did very well, for well into 1916), how about the Balkan front? When the Allies landed in Salonica and Bulgaria was lost to the Central Powers, how could the Ottomans defend Istanbul? Once they lost the war, obviously the Allies would share the spoils; i.e. the Ottoman lands, starting from those parts with an Arabic-speaking majority.

So my conclusion is that yes, the Arab Revolt did not defeat the Ottoman Empire by itself and the British would likely win even without the Arab Revolt, despite being defeated twice by the Ottomans (once in the Gallipoli campaign in 1915, and then in the Battle of Kut in mid-1916). The war was slowly but surely chipping away at Ottoman resources (both financial and human) and the Allied landing in Salonica would change everything drastically even if it were not for the British advance in Palestine and Iraq from 1917 onwards. But this does not mean the Arab Revolt was 'overrated' or irrelevant, since it did make the life of the Ottoman Army harder, harmed the Ottoman ideological and political stance, and had important repercussions for future relations between Turkey and the Arab states.

I hope this helps and let me know if you have any further, more specific questions!