This is not a quick, simple process. You don't need to just move your factory equipment from one building to another one on the different side of the border. You'll need to train new workers and quality staff, you'll probably need to adjust your supply base, you'll need to validate your processes. China still makes most of the consumer goods that an average person has, and it will continue to be that way for a while. They've spent decades creating an ecosystem of manufacturers, and that can't just be replicated overnight
It remains to be seen exactly how Europe will go in regards to dealing with China. I think that will have a considerable impact on the extent of China's economic isolation, if that is to be (assuming they don't liberalize access to their economy and end various negative trade practices).
Obviously most of the major economies of Europe are increasingly debating how to handle China. In terms of potentially limiting China's access to their markets, limiting the ability of China to buy their companies, forced technology transfer, and so on. The outcome of which way/s Europe breaks on this topic is an interesting wrench in the whole thing (eg Western Europe might put up further defenses, while parts of Southern Europe and Eastern Europe + Russia may go more heavily with China).
If you're eg German automobile makers or Italian & French fashion / cosmetics companies (LVMH is drowning in Chinese sales presently, making Bernard Arnault worth nearly $100b), you desperately want to maintain full access to China at low tariffs.
Germany (the most powerful country in the EU) is particularly benefiting from trade with China, which also doesn't bode well.
I would love for it to turn out otherwise though.