I think the Gallipoli campaign was felt more of a disaster by the ANZACS was that it was their first real "blooding" in war. They had sent troops to the Boer War but casualties there had been relatively light. The casualty rates at Gallipoli were high and many communities lost what almost amounted to an entire generation of their young men.
In Eric Bogle's song "The Band Played Waltzing Matilda", the words "They gave me a tin hat and they gave me a gun and sent me away to the war", are inaccurate. One of the reasons for the high casualty rates was due to the fact that the troops did not have "tin hats" - they were not universally issued to British troops until late 1915/early 1916. The incidence of head wounds caused by bullets, shrapnel and rock splinters was far higher in Gallipoli than in France, this hastened the introduction of "the Tin Bowler" to British and Commonwealth troops.
The campaign, though considered a disaster, came tantalisingly close to succeeding. It opened with an attempt to force the Dardanelles with naval forces. At the time the Allied naval commanders issued orders to withdraw, the Turkish shore batteriies had actually run out of ammunition. It was then decided to land a force so that a combined operation could be resumed. In my childhood our next dooor neighbour fought at Gallipoli and later in Palestine under Allenby.
What you state regarding the proportion of troops participating is correct.