Not all markets, and not even all European markets, assume a single trading zone (i.e. a copper plate network). Re-dispatch costs are high because policy choices have created a physical reality that drives high constraints.

That could have been prevented by simply not permitting connections in certain parts of the network. Yes, theoretically it could also have been prevented by forcing generators to directly bear re-dispatch costs which would have led developers to build a different set of generating assets. This would have been a different set of market mechanisms.

However, if generation decisions had been made centrally, they would have been made by the same system operators, regulators, and governments that mandated the construction of the current system and they would have therefore built the same system more or less. Do you really think that if e.g. Germany or the GB network had been centrally planned by their respective government mandated regulators and system operators, they wouldn't have put all those windfarms exactly where the market-led model we actually have has put them?