This is so ill-defined as to be useless. If by Marxist we are speaking of what mark (and Engels) wrote, then it must be pointed out Marx was against equality as a metric or measure. And that, contrary to popular belief, he did not originate collectivism and egalitarianism, but heavily critiqued the proponents and thinkers of such that existed in his time.
https://anarchopac.wordpress.com/2017/09/07/marx-and-engels-...
> equality of opportunity
Interestingly enough, this is another way of saying no equality at all. That is, the outcome of the competition is, by and large, predetermined. Children born into affluent homes will be sent to better schools, have better tutors, have parents who understand such social systems, and even posses such (seemingly minor, unless we of course want to talk about brain development) advantages as being fed enough nutritious food as to not be hungry. The athlete with access to experts and money and training (and time to spend otherwise not having to earn a living while they train) will outperform the runner who gets in a couple miles after work. (This, of course, extends to everything aspect of business and life. I'm sure there are many people who, if they're parents had had a few extra hundred thousand or million dollars to invest in their child't first few failed businesses, there are a lot of people who could be "successful".) So if we want "equality of opportunity" the first thing we have to do is divorce parents and children in something like Plato's creche. Otherwise we must admit that the system is built not on allowing the meritorious to rise (with whatever definition of meritorious we employ) but instituted by a power class to maintain that same power class.
> plays the game
When survival is on the line, how is it rational to 'play by the rules'. If someone existed in a post-apocalyptic wasteland, would it be rational to to hand over their family's stock of food on the outcome of a chess game?