The irrational way of ressource allocation and oganization of production inherent in capitalism leads to wasted economic potential in pursuit of personal gain and profits, instead of democratizing the workplace, improving living standards and reducing work hours. We waste the potential found in automation on producing mostly useless things that are designed to break in a few years, while also threatening the job security of countless of working people instead of shortening the work week with same or increased pay.
And lack of competition and motivation due to lack of competition. Then upper tier class still exists, still takes all of the money. Product, quality of life becomes a hollow shell, unsustainable then collapses.
Oh that's happened many times the world over. Guess someone didn't learn from history.