The purest Capitalism is Unregulated Capitalism: Regulated Capitalism means that there is some other ideology (in the basic sense of “set of ideas”) guiding the decisions about the where and how to regulate said Capitalism and having the power to impose itself on Capitalism (otherwise it wouldn’t be “regulating” it, just “advising” it, which would be promptly ignored).
The problem is exactly that the dominant political system we’ve had for the last 4 decades, often known as neoliberalism, is all about removing regulations on Capitalism (hence neoliberalism), so a movement to make Capitalism the one and only political ideology with any real power for every and all political decisions in Society, not merelly the one related to Trading. This is why it’s now common for mainstream politicians to hard all about “doing what’s best for businesses”, unconditionally and never once using the caveat that Society should only help businesses which are good for Society.
The problem is exactly that we’ve been moving to 100% Capitalism, with not other ideology providing oversight over it.
Maybe Capitalism does work well as a means to optimize resource allocation and bottom-up economic coordination for optimal results in some markets, but it most certainly doesn’t work well at maximizing outcomes for the greatest number, in terms of systemic survival (Capitalism brough up Polution, which it most definitelly wasn’t solved by it, and now Global Warming) and doesn’t even seem to work well in markets which aren’t highly liquid with no negative externalities (i.e. naturally very competitive and non poluting or otherwise damaging).