Yes, you are absolutely right. The paradigm shift that occured between WW I and WW II is one of the biggest in the history of warfare, comparable maybe to oblique order in ancient Greece or the invention of the stirrup in the 11th century. (Not that there were conflicts between WWI and II such as the Spanish civil war that already saw some of the changes, but I will ommit them for better comprehension, it's not really that important)

Before WW II wars were dominated by men on foot and men on horses for thousands of years. WW II changed this to war being dominated by men inside of machinery, armored vehicels and aicraft to be precise.

Now both of these types of machinery saw use in the WWI as well, tanks being invented in that time. But why?

The reason for this is the special circumstances WWI was fought. In the century leading to WWI warfare saw some changes in the equipment used and subsequently in the tactics applied. The water cooled machine gun, the precise, magazine fed rifle, long range artillery with explosive shells.

All of this innovations made the soldiers very vulnerable compared to earlier times, yet at the same time made proper protection hard. You can't just make armour protecting you from precisely fired bullets, it would be too heavy. So starting in the middle of the 19th century, infantrymen started to dig themselves in. Being in a trench protects you well enough from artillery shelling and rifle fire, because you limit your own exposure. In WW I trench warfare saw its height. The armies fighting were large, well equipped with machine guns and long range artillery and had absolutely zero ideas how to overcome staggered system of trenches.

In the beginning they did what you said : They just charged. But soon they noticed that this makes zero sense, because having infantry or cavlary charing at a dug in machine gun is...well it's like trying to knock out a world class boxer by throwing gummy bears at him.

The first thing the officers tried were destroying the machine gun positions with artillery. This led to a situations where you'd shell the enemy lines for hours to try and then attack empty positions. It didn't work too well, the defending soldiers just hid in bunkers or fell back (even though artillery was one of the biggest killers on the battlefield). Other inventions, both tacitcally (strom troopers [yes, they were actually called that way]) and technical (gas) did not lead to overcomming the trenches either.

Now one particular idea that saw the light of day were tanks. A tank was basically an armoured car that carried a gun and made it possible to precisely attack machine gun positions and make infantry attacks possible. They were a major change and could potentially shift the way the war was fought, but the war was over before they saw broad use.

In the times between the wars, all nations build tanks an integrated them into their armies. Most of them were planning on using them as supporters of the infantry, like in WWI. Some tacticians however (most notably Guderian in Germany and de Gaulle in France) wanted to create special tank forces that breached the enemy lines and carried the weight of the battle themselves. Well Guderian was succesfull with this idea, de Gaulle not so much.

This led to the situations were in the early stages of WWII, Germany had a huge operational advantage over the allies. Their system of tank divisions attacking concentrated to create breaches, supported by aircraft such as dive bombers, and having the infantry follow to secure the flanks and fight enemy in areas tanks couldn't do so on their own (Urban areas, forests etc) was what gave them the victories in the beginning. Well it was a major part, together with tactical and operational flexibility, a certain ruthlessness and a fair share of luck.

This way of fighting a symmetric war was called "Blitzkrieg" due to the high pace and is to this day the basis on which armies prepare to operate.

(Note : On a tactical area it's usually referred to as "Combined arms", which is also the term used nowadays. "Blitzkrieg" usually refers to the way the Wehrmacht used this way of the "Combined arms")