On progressive taxes: my apologies, i wasn't very clear. Yes I'm familiar with how it works, I just meant raise the bottom tax bracket. EG: first 30k is not taxed.
On economic systems: there are negative trade offs with scale, central planning, vertical integration. Less diverse ideas, can be slower. There are still middlemen just structured differently.
I'm not against publicly owned companies though, they should tend towards infrastructure and natural monopolies (rail, telecom, probably some tech...)
I disagree that it would be easier/more efficient to break up companies than to tax them as they approach that state of need. But I'm not against the idea.
Lower population in of itself is a good thing.
It's the change that is disruptive and will cause suffering in ways that are unique to the suffering caused by over population.
As population growth slows, the younger generation needs to support more elderly. Which means we need some combination of:
Working population being more productive. Population making do with less.
However you approach it, there will be segments of the population that are very unhappy.