works very well, one of the few things i can credit MS with. Of course it is not invulnerable, but quite close if properly set. and if on top you have good security habits, being infected is almost null.
Indeed, the only case they would work is that you don't do anything on your computer and keep it in the same state before those tools are installed (which is out-of-scope of 99.9% of home users).
As long as people have the attitude that they should be able to do what they want on their systems, then security will be broken. And that won't change until the Earth falls into the Sun and man and digital devices are no more. Period.
People are always the source of their own problems.