Boring explanation: The return on investment in developed nations is much lower than in developing nations. Companies invest abroad and avoid hiring domestically. This has resulted in a flood of cheap consumer goods from China and other Asian countries which enters developed countries. Americans don't have to work but they also don't get paid unless they own stocks in these multinational companies. Interest rates go down as inflation goes down. The country now has a surplus population of low skill labor that simply isn't needed anymore. As I said, if they don't work they also don't get paid which kills consumer demand and the lack of consumer demand then further reduces the need to invest. The winners of globalization end up with more money than they know what to do with so they just invest it at any yield. More investment with the same returns just means less yield. This means interest rates must go down as well.

Now here is a problem. We live in a physical world. Monopolies, extortion and violence exist and if you use them properly you can force yields to be roughly constant. You can achieve higher yields by screwing over other people. The most common examples are housing and medical bills. If national yields are 0% and your house gets 3% yields because it's location is a monopoly then you got those 3% at the expense of another person who is losing those 3%. Since the level of production and amount of money did not change, inequality must grow.

In that sense interest rates aren't the problem. The real problem is that there are investments whose yield does not follow the interest rate plus a risk premium according to the asset class. If housing yielded 0% then only those who actually want to live in it or rent it out (for a fair price) would buy it.