Stop fighting with the man in your head and actually engage with the argument. Private for profit companies inherently optimize for profits. Dealing the pollution costs money, so they don't do it. This is by design. This is a bad system, and it will never work no matter how much duct tape you throw at it.

Neither government agencies or crown corps are perfect, but at least they're not inherently flawed either. Yes they're subject to different circumstances than market companies, but that can be dealt with. Capitalism's inherent drive to cut corners and destroy the environment can't.

Even if the water companies were state owned, dealing with the pollution would still cost money and there are a bazillion other demands on the state's finances which are more pressing than keeping rivers clean, such as providing healthcare. This isn't a hypothetical. Scotland has a state-owned water company, and it'd be impossible to write an article like this about theirs not because they're doing better - all indications seem to be that that they're not - but because it relies on information from monitoring equipment that just doesn't exist there. It was pretty recently added in England too, over the last few years, so it's clear that the Environment Agency does actually care about this... not that you'd even know that had happened from the UK news coverage, especially the Guardian's.

Other places in Europe seem to be even worse. For example, I've seen people from Ireland shocked that thsi would happen and preaching the benefits of their state-owned water and their fight against privatisation and water billing. There are places there which literally have no sewage treatment plants still. As in, their sewage goes straight from their houses into the rivers and the sea untreated, not because of a fault or undersized treatment plants or heavy rain ( all of which they have problems with too) but because the sewage system is literally designed to do that 24/7. The government was meant to have fixed this decades ago according to EU rules but has kept dragging its feet on building sewage plants. And they're probably not unique - they were literally the first country I checked, and the second, Spain, had the same issue as well.

If your entire argument is "better things aren't possible" and "it's bad in other places too" then that's pretty weak

No, the argument is that nationalisation/privatisation is irrelevant to the problem at hand. There is no causality, there are plenty of examples of well-regulated private companies and disastrous state-owned ones. There might be a correlation, but you didn't show any numbers to that effect.