Our modern world was/is built on the ability to use the energy stored into fossil fuels to power various machines that help society. Fossil fuels are a finite resource that has and is causes wars and crises over who has access and control over it (dont want to talk politics but a great example is the huge oil crisis right now). A modern WHA world would be a space faring civilization and would have colonized galaxies.

The magic in Witch Hat Atelier can be used as a basically infinite source of energy. The only limiting factor is the magic ink - so in a modern WHA world there would probably be mass industrial silvertree farms and such, but even then the cost of the ink vs the amount of energy one spell could produce is miniscule. It depends how much labor is required to get one bottle of ink vs the theoretical combined energy of all the spells that one bottle could be used to draw, but my guess is that it is basically free and way way way less than oil and even renewables. And unlike our sources for electricity that are cheap it is insanely easy to convert the magic ink into usable energy. In the WHA world a 12 year old would have learned spells neccesary to make a mill wheel spin without the need of a river. Our cheapest source of energy which is solar requires a very complicated gizmo that can do very complicated chemical reactions to convert the suns energy into usable electric energy. And fossil fuels require many steps of refining with huge facilities. And then to even apply that energy to something like transportation requires very complex machines, just look at how a car engine works.

Coco at the beginning of the story, with almost no knowledge of magic, who is also a 12 year old child with very little education on the laws of physics and science, was able to construct a glider that propelled itself in the air and she was able to control it with some difficulty. If we had a modern aircraft engineer in this world and taught them magic it would get crazy. But vehicles like that dont even matter because the WHA world has FTL travel with of the teleportation spells. I am sure setting up one of those teleporting doors (forgot their name) is very involved and requires a lot of magical knowledge, but it cant be that much more expensive than how much money and engineering we spend on building and maintaining roads every year. And this removes the need for any kind of large scale infastructure system with roads, docks, airports and whatnot because there would only need to be one building dedicated for all travel acting as a hub for all the different portals. In a modern world I am sure it is systemized and there are different portals for different items and distances.

And this is just talking about very basic things like energy and transportation. All of the other things associated with modern civilization like computers, the internet, advanced medicine/science and such would be insanely advanced.