But we don't make phone cases in EU. Neither most of the stuff actually sold by aliexpress. Our local "phone case stands" in shopping centers sell the same cheap made-in-china stuff as on aliexpress but they want 15-20euros for the same cheap case that is 1eur on aliexpress (+10-15 for the screen protector, etc). I mean sure, they have to pay rent for the space and they have to pay the worker, but they're just a middle man, they produce no real value (except to get the case faster).
So, back then, i'd pay 1eur and get the case (a bit later 1eur+vat), or 4eur (+vat) for all the items. I'd have money left over, that I could spend at a local restaurant, where other people would get paid, for cooking and serving me a meal (and farmers before that). (i won't give the "save to buy an apartment" example, because none of the EU states is actually doing anything to make that peossible for normal people, quite the opposite).
And now I either pay a lot more money to the government (and get notting more back from them), pay a lot of money to a reseller/dropshipper, and get the item a week earlier than from aliexpress. There will be no european phone case company to take over that business, the just 'stuff' will be just more expensive, and we, europeans, will be able to afford less.
And yes, I know, aliexpress will adapt, they'll build warehouses in EU, and iphone cases will be shipped from romania or hungary or somewhere, but they'll still be more expensive. And that's just phone cases... if you have an iphone, you'll find them in aliexpress warehouses locally. But what if you want custom electronics only found on aliexpress? Some niche esp32 board? Some salved controller for a retro computer? Can you count on aliexpress storing those things in EU too? Or will your other hobbies become much more expensive too?