I think the criticism is valid, not in favour of cars but in terms of future sustainability. Public transport infrastructure needs investment to keep it growing and improving. There is a risk with a free system that the focus in each budget is the battle around just covering the day to day costs, and the future investment gets put aside constantly as a problem for another day. This is typical behaviour of politicians, and makes the public transport organisations entirely dependent on politicians for their budget.

However that problem applies to a lesser extent with systems that do get revenue from users, it's just that they are less completely reliant on politicians and their yearly budgets. It's ultimately all about political will and a willingness to prioritise transport investment over other public spending.

I do think the scheme is a good thing, I'm just dubious that the political will to sustain it will persist long term. However hopefully this will spread to other European cities and whole countries and so become a normal idea alongside investment for future expansion and upgrades.