Or is it just that more people want to invest than ever and are seeking yield/return in whatever they can get their hands on? Isn't that a good thing that lots of people have "disposable income" they want to temporarily get rid of? Why does it need to be this doom and gloom "big bubble all over the place" thing?
Low interest rates are supposed to fuel growth of productive assets. Creating and expanding businesses that create products and services that people want.
Instead, disposable income and cheap credit are pouring into things like crypto, meme stocks, and sneakers. No new value is being created. These 'assets' only continue to increase in value because of currency devaluation and ponzi scheme like effects, i.e. new people jumping aboard the 'get rich quick' train.