The process for migrating eSIMs for me has never been easy and has always taken 1-2 days and repeated contacts with customer service agents to actually work. Compared to the 10 seconds of swapping a physical SIM. I'm sure there isn't an inherent technical reason why eSIM couldn't be just as easy if not more, but I assume it's another case of enshittification.
The "inherent reason" is that user freedom isn't allowed in SIM land, basically.
eSIMs are designed around "the user is the attacker". So you can't do things like transfer profiles from one eSIM to another offline, by design. What the "transfer" really does is kill the old profile and issue a new one for a new eSIM.
It still could be designed for less user friction. But the whole ordeal could be avoided if eSIM wasn't designed to be user hostile in the first place.
Agreed, the rest of the comments are delusional. First, you have to contact customer service, which takes a few days to get a response. Then you have to have another device to display the QR code on, which you won't have if you're travelling. They'll send you a QR code you have to scan with the device you're currently on, AND you'll have to do it without an internet connection. Meaning it just doesn't work, at all.
An offline device can take a SIM card just fine. But if you're setting up a new device, or setting up an existing device on a new country on eSim, doesn't matter, you can never connect, because you have to already have internet, to get internet.
Esim was a good idea, implemented so horribly it's worse than the 30 year old predecessor.