This ability to think critically in day-to-day situations is sometimes dubbed "street smarts"
Materials, jargon, equations, theories, or histories of difficult and heavily guarded academic subjects, make critical thinking more complex and much more difficult, and it requires much slower and more deliberate mental moves.
Writing is the tool that we use for that, as it is a way for us to store our thoughts on a page, change and rework those thoughts, and then eventually come to rational and informed conclusions.
This means that critical thinking happens on the page. When we draft and then revise our work, we are doing the slow work of critically thinking about it.
We can think about anything.