Generally, the importance of logistics has grown over time. While I cannot speak about contemporary military logistics, logistica came into importance during the Napoleonic Wars where everything from orders to supply was militarized and simplified.

The best example is during the 1806 campaign when Prussia declared war. Napoleon was able to pull several corps from Germany and Austria into Southern Poland and Silesia in a matter of a few weeks whereas the Prussians had trouble mobilizing within their own country.

The biggest thing to contribute to French movement is the heavy use of foraging, where food was procured locally rather than from supply train, and the use of roads to by corps to spread out the army and allow better movement due to the army moving in a broader fashion

So logistics became important because it allowed France to out manuever their enemy.

More important than ever. Keep in mind that militaries in the past paled in comparison to the size of militaries today, much less the militaries in the world wars.

Many would argue that in WW1, the Germans miscalculated how quickly Russia and France could mobilize, thus causing the Schlieffen plan to fall short of its goal to knockout France early.

In WW2, much of the Battle of the Atlantic was to cut off logistics to Britain. Likewise, may air attacks were targeted at railways and transport ships. Air Superiority gave the Allies unfettered supply chains that the Axis did not have the luxury of.

But, the best example of this is in modern militaries. Actual number of people in combat arms roles vs. support roles is smaller than ever. That means fewer troops are actually being trained to just fight - many are logistics experts, technicians, mechanics, etc. And for the US military, the dominant military force in the world right now, the emphasis placed on logistics is staggering:

The Air Force maintains 300+ strategic and tactical transport aircraft. At the height of the Cold War, the AF could move an entire battle-ready division to Europe within days of the start of hostilities.

The Air Force maintains 400+ aerial refueling tankers, meaning that aircraft in the US could operate anywhere in the world without needing forward bases to operate.

The Army has over 2000+ utility/transport helicopters. The Marine Corps has another 200+ heavy lift helicopters (capable of carrying 50+ troops or 20,000+ pounds of equipment each) and 360 Ospreys planned.

The Navy's Military Sealift Command (they run the USNS ships) has over 100 ships doing anything from sealift to combat logistics support to being dedicated to supplying submarines.

While the relative complexity and scale of military logistics has increased, I would argue the actual importance of logistics to military success has not varied throughout the history of warfare. Logistics have always been a central aspect of war, if not the most central aspect. No army of any size, whether it's a small raiding force or a massive invasion fleet, has ever been able to ignore the inherent logistical problems of assembling hundreds or thousands of men and transporting them great distances in order to participate in combat. Humans need food, horses need fodder, missile weapons require ammunition to be effective; the list could go on and on practically forever. Without logistics, there is no warfare.