In my career as a software developer, you become invisible at 30. You might be the most skilled you've ever been but finding good opportunities becomes harder than ever. The worst part is that this ageism occurs at the expense of everyone. In the past few years, many people noticed that software has become increasingly buggy and has suffered from an increasing number of hacks. I think it's partially because of age discrimination. In this industry, I believe there are more skilled people without jobs than there are skilled people with jobs due to ageism.
This article underestimates the extent of the problem and how much worse some people are affected. That said I don't think the problem is ageism only. I think the problem of our society is all kinds of discrimination. Because it is fundamentally unjust in its design (e.g. monetary system and tax system), it discriminates against people as a way to allocate resources. Discrimination has replaced the free market mechanism and dishonest people are rewarded at the expense of honest people. People of older generations have no idea how bad the problem is. Young ageist jerks are the least of our societal troubles.
Look at what kinds of young people are succeeding and taking up all the influential roles in society. The moral decline has been swift. This cannot be good.