War economy vs consumer economy. You may need to give up some iphones and other luxury things if you want to hammer those 3.5m shells in that short time frame. 😁
It's not a problem to consume that amount of ammunition, you just need 'a few' barrels and men to operate them but I'm pretty sure they didn't produce 700 000 shells per hour.
But yeah, the manufacturing capabilities of whole Europe is a poor joke right now.
What the previous poster was pointing out is that the manufacturing capabilities of Europe would be more than capable of handling this task, if any significant percentage were applied to it. As it is, ammunition for 155mm artillery pieces is not something that there's usually a heck of a lot of demand for, so it makes up a vanishingly small percentage of overall production. And modern factories, because of how things are built now, are much, much harder to just switch over to making a different product. Even if they wanted to, Germany could not easily give over a significant portion of their national manufacturing capacity to shells without it taking years to do so.
Back then 13 cm, 15 cm, 17 cm and 21 cm artillery cannons were in use, so the shells were not necessarily significantly smaller. However, modern artillery shells surely are more complex involving microelectronics or even rocket propulsion and the use of modern explosives makes the 'boom' also bigger.
In terms of modern shells being more complex in general: yes and no. modern shells pretty much always use some kind of electronic fusing, sometimes multiple kinds of electronic fuses. back then they had bombs, mines and grenades with literal clockwork inside and electronics was still very rare. also fuses and primary charges were not easy to produce reliably.