I could be mistaken, but I recall reading that there are quite a few hoops to jump through before you can fly for the big boys. For example, you would typically start with shorter/less important routes on smaller airlines. Also, the pilot unions keep the good routes (and salaries) for the more senior pilots, so tenure plays a big part in how much you get paid.

I’m hardly an expert, but I understand it could take 15-20 years of a flying career before you reach the point of being a “first-year captain” at a major airline (the first column in this chart).

Yes, exactly. Expect to spent at least 10 years as a first officer before getting a shot at Captain. I’d wager that Covid has pushed that out to 15 years. I have family and friends who are pilots, and the landscape is brutal with yearly pay rises falling far short of inflation in a lot of cases, and bonuses being minimal or non existent for the last few years