Anybody who bought bonds in the last 15 years is underwater. Portfolio managers who pleaded with clients that 60 - 40 balanced portfolios were conservative didn’t understand that money was free and had nowhere else to go. They should be fired.
Bonds are ok if as an individual you have a long enough timeline to wait until maturity—but of course the longer the term the more opportunity is lost.
The problem today is that we may get both a stock market and a bond market crash at the same time—hard to do but with a decade of free federal reserve money even the impossible becomes possible.
For businesses who may need cash at any time bonds can be a disaster waiting to happen.