My negative experience doesn't compare to Ms. Fowler's, but what I've seen basically boils down to:
1) Senior engineers and managers who lack anything approaching maturity. A lot of toxic personalities have been promoted into positions of seniority because they were at some point considered high performers. Many managers and senior engineers are concerned mainly with expanding their influence over improving the organization, helping those with less experience or — god forbid — actually getting anything done.
2) Diseased work culture. 60-hour work weeks seen as normal and encouraged as an enactment of Uber's "Always Be Hustling" cultural value. Tons of drinking, sometimes forced on you by your manager or your manager's manager. Too many unhappy, burnt out people fearful of negative performance reviews.
3) A lot of this stems from our CEO, Travis Kalanick, being profoundly out of touch. He's constitutionally incapable of acknowledging the company's real problems (toxic culture, massive unprofitability, drivers who hate us to name a few).
There are some fantastic engineers and plenty of good people at Uber, but the company rewards the bad eggs far too often and it's killing us from within.