I'm not sure they used the word celebration, but it they did it was probably meant in older sense of marking an event than the newer sense of being happy about it. Celebration and commemoration have the same original meaning and derivation.
All TV is natually light weight, limited on facts and big on happy encouraging titles. This was as much a programme showing laser cutting and what a bearing is. The information about the Battle of Cambrai amounted to the Tank battle going better than expected and the organisation not being ready to exploit it (the Cavalry BTW were very effective in 1918 and the Russian revolution, they were only an anachronism to the 1960's historians who didn't remember how many more farriers there were than mechanics). They barely mentioned the evolution from the Somme where they had the tools but no experience how to use them through to the hundred days to the Armistice where they had it working as well as it could without portable radios.
I would not describe the First World War as needless. The people at the time were certainly in favour of not having Prussian Generals running the world. They lived in awful conditions for sure, but got on with it, must have been somewhat used to it and were really making efforts to improve. The Second World War can be viewed as the continuation after the German revolutions of 1918 and 1933 in the same way as the French Revolutionary Wars lead into the Napoleonic Wars. The whole series leads Europe to stop short now we have the means to destroy ourselves and agreeing a balance again between France and Germany (Austria exists as the counter weight).
Would you get upset when they show Sharpe on the telly (bad acting and repeats accepted)? About 2 million died in that bit of human endevour. We are not a friendly species.
Andy