The economy has never worked like that. When you increase productivity, you create wealth and you enable other industries to appear. We have gone through numbers of those cycles. The industrialisation of agriculture, then machines in manufacturing, then introduction of computers (think of all the secretarial jobs, computers - as in engineers making calculations, accountants that have disappeared), then outsourcing of the industry to China. But somehow unemployment is low in most western countries. So what makes you think this time it will be different?
Western employment has survived because automating and outsourcing labour has pushed people to take up knowledge/services work.
If AI is somewhat successful at automating knowledge work, what feasible job could exist that doesn't require your mind or body?
Services like healthcare and plumbing aren't going away of course, but there's not enough demand to support an economy on those jobs.
In my opinion the whole economy needs a rethink regarding what our actual goals are as a society, and maybe AI will force that conversation to happen, but I'm sceptical if it'll be a well-considered consensus.
If it's no longer being maintained then put a depreciation warning and let it break on its own. Changing a deprecated feature just means you could maintain it but don't want to.
Alternatively if you want to aggressively push people to migrate to the new version, have a clear development roadmap and force a hard error at the end of the depreciation window so you know in advance how long you can expect it to work and can document your code accordingly.
This wishy-washy half-broken behaviour doesn't help anyone