The thing that's different this time is the accelerating impact technology is having on the supply/demand curve for human labour.

As machine labour, A.I. and technology enabled globalization eliminates the need for human labour in more and more industries, the excess profit is passively migrating to the owners of capital. It's a stealthy contributor to ever increasing inequality and one that doesn't respond easily to conventional approaches to mitigation.

A 90% top rate for income taxation may have worked in the early 20th Century but that was before it became so easy (because of technology) for individuals and corporations to change domiciles. Unfortunately, those conventional policies will prove no more effective than "pushing on a string".

We need 21st Century solutions to 21st Century problems.