Because developed countries have access to effective vaccines and natural immunity built up during breaks in lockdown (which didn't compromise the vulnerable as much as a no vaccines herd immunity strategy would have done).
China doesn't have access to effective vaccines.
There are also many other reasons why countries cannot copy China, political, economical etc. African countries with simplistic economies and more people living in absolute poverty or closer to the poverty line couldn't actually fully lockdown even if it was necessary.
Except omicron is effected by the vaccine if you have had two doses plus booster. Your point is simple, because it isn't 100% percent effective it isn't effective at all. Nonsense. Sit down again.
Three US studies offer more evidence that third dose of COVID vaccine is highly effective against Omicron.
www.aljazeera.com
For many reasons, logistical, economics, political. Not many that are valid excuses though. Isn't an easy thing to do though, particularly when you have the current naked mess in number 10.
Why do you think politicians the UK and USA would feel responsibility for community transmission in other countries?
But officials Europe have felt responsibility for pushing back against new variant transmission when they felt it could be avoided or delayed.
That's no longer possible in the UK but don't discount the possibility of a new travel ban when one pops up again.
I actually think that the patents should be suspended and vaccines should be produced at mass scale license free. But that's a different issue.