I agree with most of what you say, Abusimplea, except possibly 'every non-competitive system non-sustainable.'
So-called communists have tried hard to establish economies wich are not based on competition and all but Cuba failed quite hard or switched to full competitive capitalism by now.
The problem with the lack of competition is, that humans are not only greedy but also sloppy as hell. They cut corners whenever possible. If they get away with not doing something right, they will just not do it right.
Competetive economies provide an implicit fitness test: Your product is either perceived as being at least as good as the competitor's - or your company goes extinct. That is why monopolies and cartels are so bad in our current economy. If someone achieves a monopoly history has shown, that that one will cease to innovate and start rising prices while lowering quality until a new competitor emerges.
In theory there could be non-competitive economies and they would feature a fraction of the current overhead. But if humans where more compatible to such an economy, than the current one - we would already have it by now. Some have tried hard and even killed people to get the remainder behave - it did not work.
Don't forget: Humans did add lead to gasoline, and therefore to the very air they and their offspring breath, knowing about its toxicity. They (again: in general) will not do the right thing if there also is a wrong thing wich is easier to do or gets them more wealth in the short run.
The state buys out all three companies and keeps exactly the same rules but without the competitive strategies thus saving money. The experts and workers are paid exactly the same bonuses and pay increases as before. Eventually the companies are merged into one nationalised industry for more efficiency, less waste on competing, and more profit all round. The only competing might be for a greater share of customer wealth from other markets but is that necessary? Why tempt the public into choosing between a new car or a luxury holiday - let them decide for themself. Especially if the state owns both industries.
State-owned companies definitely work for well-defined and non-subjective goals like "reliably get water to and from every building in the district" or "when something burns, quench it as fast as possible", wich have a high need for reliability. But state-owned companies come with a surprisingly high overhead cost. Workers and management seem both to get less work done in state-owned companies so you need more of both. It could be the lack of risk for going bankrupt - and therefore the lack of a percieved need to be productive.
The other idea I had I've already mentioned: private companies controlled by a quality incentive tax (QIT.) They all continue to strive for wealth but in a different game. The goalposts have been moved. To increase profits they must improve products and services thereby reducing their taxes.
That could work if quality is measured accurately. But that in itself seems to be surprisingly difficult - even when it comes to the milage and pollution production of cars which i expected to be rather easy...
I don't think, it is possible to really change economy much without changing the humans first. We need better education for our children, wich after some generations will then change the economy gradually because they themselves socially evolved to beeing less greedy and corrupt than our generation.
I hope, they will also find a cure for the antibiotics-resistant pandemic that made them live in the domed cities...
They surely will agree with us, that giving all sorts of antibiotics to chicken to make them survive mass-production facilities long enough to get them to market weight was totally worth it.