For the complainers, it's honestly not that complicated. Don't build when you don't have the workers or can't tolerate the shift.
Just like we have to accept that we don't get to tell each ship where to go and what to fire on during battles, in the economy, we don't get to tell each worker what to work on. Instead, we set up our system to optimize the conditions that lead to better or worse outcomes from the parts we don't control. When building a fleet, you pick a range of ships, weapon types, etc. so that when battle happens, you'll likely have a positive outcome. Think about economy the same way and you'll have a much better time. Except in the economy, you still have far more control than in battle.
My first few 2.2 games, I struggled with unemployed pops and giant economic shifts. But once I understood the system and stopped overbuilding, I have much much fewer problems with pop employment and demotion. I also make use of the market where short term mismatches in workers still cause problems, so that I don't end up in a tailspin. Use the tools available and stop expecting the game to play like 2.1.
That said, I do think there could be a delay for pop promotion (albeit short), and a decrease in the demotion time. That's a balance/tweaking concern, not a fundamental problem.