It is not like if you see ambition as something less than a moral good you will no longer get anything done. You will just turn off this useless modeling of future events in your head.
I suspect in our culture, ambition causes nothing but useless pain and is counter productive at the average as people model their future life up to these highly improbable lottery winning situations.
Climbing Mount Everest is really the best metaphor. Massive risk for basically no reward. The whole idea is objectively stupid but seen as some great accomplishment in our culture.
Let's face facts. If our ancestors never had any ambition we would still be hunter-gatherers. We would probably have the same level of happiness and sadness since we would never know anything different. Flowing through life is a choice that works for some.
There's a culture that pushes us to "dream big" (e.g. build a unicorn startup, become a billionaire). That's usually awfully ambitious, and as feasible as winning the lottery for most of us.
We should be pragmatic about our life goals. They should be ambitious, but achieavable.
Even if we don't control a lot of factors in our lives we at least have the power to influence them, most of the time it comes in the form of "trade-offs". So you've got to be prepared to make some sacrifices in the present for making progress towards a future goal.
I also acknowledge that some of us have a head start due to our social/economical background, and we should be grateful for that.