[ZeroGravitas]

There is some theoretic academic suppport for tight regulation of the "natural monopoly" parts of the network and allowing competition on top of that.

The UK has leaned more towards the pretend visible competition and underinvestment behind the scenes while allowing profiteering, but even within that there's some room for innovation.

Really boring improvements like saving money on admin by getting customers to pay via Direct Debit or using the internet for customer service were often pioneered by small companies which then forced others to follow to compete. Could a well run nationalised company have done that too. Yes, but they'd have been sabotaged and attacked for political reasons, so in reality its possibly an okay compromise.

Bulb is a good example. Good customer service, non predatory pricing, supporting renewables. Broken by weirdly anti-market moves from a conservative government to patch up other anti-market decisions they'd made to subsidize fossil fuels.