My counter point to this is fairly simple: luck is always a factor in life, an unavoidable one. No matter how hard you work and plan, if a company doesn't have an opening in your area of expertise you're not going to be able to advance in that area. You can develop additional skills that qualify you for other positions, attempt to find other ways to move up, etc, but some things are just going to come down to timing.
There's nothing wrong with this nor is it something you can change. It is something you can mitigate with proper planning etc, but there is always going to be an elemental of it in everything you do. The real trick is exploiting it to its fullest when those opportunities do arise.
True, it's always a factor, but statistics and persistence covers it.
You might have say, a 5% contacts of getting a job through contacts every month. Or if you searched for jobs full time, you could have a 15% chance of getting a good job from job searching, and none from contacts that try to poach you. Most people will look at this as about the same odds... 10% is not worth the risk.
Over 6 months, the person who waits and hopes for a better job will have a 26% chance of getting a better job. The one who quit will have a 63% chance of getting a better job. Thanks to statistics, the person who persisted in looking for a job now has a 37% advantage, and good odds. They may still get unlucky. But if they kept persisting, the odds over a year would be 55% vs 86%.
There's the cost of quitting a job and staying unemployed - lack of a salary, lack of a portfolio, no contacts. But there's also the cost of working - dealing with an abusive boss, using up time and energy.
One doesn't simply look to Luck and say, "I can't risk this." Instead one looks to Statistics and decides, "Which will cost me more? Waiting for things to get better or taking a loss to try and make it better?" and make the decision on the spot, until the factors like probability or cost changes.