With handwritten labels the postal service at the shipping end would have to read them and push the data to an electronic system manually.
In Finland handwritten customs labels are still allowed, but you need to register the customs data online since Dec 2020 (or the cleark can do it at the counter).
Currently (https://www.posti.fi/en/customer-support/sending/country-inf...) there are 20 unreachable countries due to COVID-19 (AU and NZ are not among them).
Your experience with letters matches mine, they take 2 weeks to Europe regularly now.
As we mostly ship letters we just sent to every place, even if they are currently not 'open'. ~95% arrived within 1-2 months or so in those critical places.
No idea what's going on over there. The rest of our shipping just got a few cents more expensive but on average just got faster the last 2 years.
Tracked letters are like 4-5 times as expensive for me, which doesn't make sense for an average order of like $20 :/