They could be welcomed into the EU in a heartbeat.
Assuming they completely changed their food and product regulations and adapted everything from agricultural and animal husbandry to building codes to match the EU overnight.
Otherwise it's more of a decades long process.
Even CETA is still not ratified because Canadian ranchers and farmers still insist on using growth hormones and have trouble dealing with European GMO tracking and labelling.
Pre-industrial societies still expected children to work from young ages. And they would often switch to adult labour in their early teens.