I mostly agree with you. Most people, whatever theory they subscribe to, are bad at their theory. There are a lot of Christians who aren’t good Christians. Lots of Republicans in favor of big government if the project is military in nature. Lots of liberals claim to care about people of color but still advocate for policies that harm minority groups. Most people simply have muddy politics because they’re more focused on other things. I don’t think it makes certain underlying theories bad just because lots of people claim them but don’t practice them. Christianity is full of great loving ideas, republicanism makes sense in a lot of ways, etc.
But I disagree that getting the government out of the way means leaving existing power structures intact. What I have learned from libertarian theory is that a whole lot of existing power structures exist (in the USA where I live) specifically because someone bribed the government in to supporting something they wanted. Take Disney continually extending copyright laws for example. Instead of getting old media in the public domain we get ever more restrictive copyright law because some corporations found it worth fighting for. Removing government in that instance would reduce existing power imbalances. So called “right to repair” laws for example provide a balance to the powers granted by government to corporations that would lock customers out of repairing their own equipment. I’ve also heard a few credible stories of instances where big corporations advocate for regulation that ends up squashing competition. Of course some kind of regulation whether from the state or by other means is necessary to avoid pollution, waste, abuse, etc.
In essence I am saying that even though there are many who call themselves libertarians who simply don’t understand the theory or advocate for its actual practice, this does not mean that libertarian theory is itself bad. I think instead that certain aspects of libertarian theory appeal to people who maybe just don’t want to pay taxes but never really learn or care about the theory behind the idea.