I don't mean we cannot beat evil - I mean that it cannot be fought; because evil is a negation, opposed to Good - and a negation cannot be fought.
Indeed, even discerning and rejecting one evil after another does not suffice to be-Good - since there are too many evils, and the business of rejecting them has no end. Only when the rejecting of evil is set aside and The Good is embraced positively have we learned the lessons of evil.
To oppose that which is evil is Not to do Good - but merely to engage in Men fighting fight Men, or evil-System fighting evil-System... because all Systems, all institutions, are evil now.
If we engage in the fight of the lesser evil against the greater (taking the side of the less evil nation, corporation, religion) then at best we merely strengthen the less-evil, which is Not actually doing Good!
Fighting to reduce the amount of evil is not positive Good. It is to support one type of demon against another; to support one version of Hell against another.
To be-Good we must forget about fighting and be-Good, join-with Good: that is, take the side of God and Creation.
We must do Good; that is to love; to pursue truth, beauty and virtue; to know sin and reject it...
And this doing - where is it done, how manifested? Well, in many possible ways, unique to each person. Different individuals will be drawn to manifest different positive Goods; for example the traditional transcendent values of truth, beauty and virtue - and their unity in practice. To pursue and real and positive value is to do Good.
Some Christians naturally want to fight and win, they want the heroic camaraderie of being part of a victorious army battling on the side of God - so naturally they seek a Good-army to join. BUt there isn't one.
Other Christians want to suffer to win, regarding this mortal life as wholly negative, a trial, a test. They oppose the negativity of evil with a negativity of not-doing evil. They embracing death to this world for the goal of life everlasting.
...Yet so long as the world is, and I am - God has a reason for sustaining them. A long as there is me and I live, here are things I need to learn from this mortal experience, and Good to be done.
But how to do Good in a world where all activity is so constrained, where so much is forbidden, punished or poisoned?
To begin with - we can be confident that there is a Good way for us (as individuals) to live, else we would not be alive. There are Good things that we personally can do, else we would not be able to do anything.
And if our life is such that we can 'only' think; then there are Good things we could thing - Good ways we could think.
We are alive to do Good; and we can always do that Good for which we are alive.