I'd argue that full on central planning was the wrong model. I can highly recommend reading Thinking in Systems to understand the problem. But the gist is that any large system will have noise, as information travels through it. So, when you do central planning the way USSR was, it becomes very difficult to balance things. You make a plan, the directives travel down to the factories and farms where production happens, there's delay in the information arriving, mistakes in transcription, and so on. Then the same thing happens on the way back up, so the picture at the top is divergent from the situation on the ground. And that leads to things like overcorrections, and plans based on false data, so the system becomes unbalanced over time. And that's what we saw happen in USSR.

Now, that doesn't mean that the idea of central planning itself is wrong. The problem is with micromanagement which just doesn't work. And this is the problem China figure out by using markets as allocators within the centrally planned system. The planners still set five year plans, they still control the commanding heights of the economy, and give overall direction on what types of things should be produced, but the details are left to market mechanisms to work out dynamically at the appropriate level. And this type of a hybrid system is proving to be highly effective.

I'll address one of your concerns, quality. People make things well, usually. More like, people make things well because they want it to be usable and durable. The only way people won't be making quality stuff is when they don't have the freedom over learning the skills they want to, choosing the tools, and to an extent, the materials they'll be working with. So, they actually don't need any additional incentive.

Demand does not necessarily be driven top-down. The same feedback systems that are in place under capitalism can be used under socialism as well. Look at a supermarket chain for example. Supermarkets stack certain items, these items are bought, an electronic inventory system is aware of how much is stacked and updates as items are run through the checkout and leave the supermarket. Taking into account the latencies of the logistic system, new items are automatically ordered at the correct time when items run low. Over time order numbers are optimized to prevent both scarcity and waste.

These are all technical problems that can be solved already right now that are completely orthogonal to the economic system. The only metric that is necessary is "demand", which needs to be objectively measured.

The way i see the issue about quality is similar to others here. I think people want to do thinks well. The only reasons why people don't do thinks well are: a) Burnout. Lack of or insufficient recognition for the effort both intrinsic (telling yourself "what's the point?") and extrinsic (family, friends, colleagues and superiors don't care and don't give positive feedback) b) Economic constraints. Superiors demand the MVP or actively demand cheaper materials/ cheaper build processes or enshitification to drive up profit margins.

Point a) is independent of the economical system and point b) is a direct result of capitalism.

I also don't think that everything needs to be centrally planned. I like chinas decentralized approach where the further down the hierarchy you go, the more concrete and granular the plans become and some things aren't planned at all but are fully delegated to markets.