During a discussion about line infantry today versus a hundred years ago, it came to be said by one of the participants that the line infantry who fought during World War One were less well trained than the line infantry of today. I put it to him that perhaps the line infantry at the time were quickly processed in order to get them to the front, whereas today in first world countries there is never any particular urgency to produce line infantry, and as such they spend more time in training. Is there any truth to my hypothesis?
As a general rule I'd say yes. Today we maintain a professional volunteer army that spends much of its time training, while in WWI most countries moved to a conscripted army that was needed in the front. But it's not quite that simple; training in WWI varied greatly depending on the country and the point in the war.
Britain, for instance, started out with a small but extremely professional military that was highly trained and had a lot of experience. But once that force was spent, you saw them move to conscription and their individual soldiers became a lot less skilled.
Germany had a good military at the start of the war that had spent years preparing to enact the Schlieffen Plan, but the 'second wave' of young soldiers was rushed to the front without adequate training, leading to the First Battle of Ypres to be known as the 'Massacre of the Innocent'.
By the late war all the powers had realized the importance of allowing recruits to receive adequate training before being sent to the front, with the possible exception of the US, who didn't have the same experience as the other allies and took quite heavy casualties for the first few months after their arrival.