central vs. decentralized ventilation system

A central controlled ventilation system does not have individual room control, at least not for the price usually charged in single-family homes.

That is wrong. The airflows can and do get adjusted in the distributor. What you mean refers to a readjustment via an actuator. Please "rant" a bit more precisely.

The ventilation ducts can very well be cleaned with a little effort if(!) it is ever necessary!

And if I have mold in the room: yes, where does it go? Into the exhaust air, through the heat exchanger, and out.

I take the liberty of quoting myself

Sometimes people here like to exaggerate to emphasize their own statements and make a mountain out of a molehill ;)

Or to justify their own wrong decisions afterwards ;)

With a decentralized ventilation system, I can control each room separately if I want, but at least the upper and lower floors separately.

Hand on heart, how many controllers do you have? One per floor or one per room?

And I simply replace a defective fan. Costs 500 EUR including heat exchanger. How much does the central fan of the controlled residential ventilation cost? ;)

Remember that each individual fan can break down and eventually will (we are talking about decades after all). 6-8 times 500€ is then not so much cheaper.

One of my Lunos e2 units is now defective after 9 years. It rattles. I removed it and put styrofoam into the hole. It's just in the office; I air out anyway occasionally through the window when I'm in there. I would clean a central ventilation system regularly; mold in the ducts is not to be taken lightly. The decentralized ones are easier to clean.

Due to the numerous advantages of a centralized solution, for example, the wastewater in the house is collected and then led centrally out of the house through a single drain.
I have never seen it that way, but let's ask what [Rottenmotor] says about it?
Probably no concerns? :D

What does ventilation have to do with wastewater? I'm completely clueless.