There are entire books written about investment strategies. This is not the place. But your comparison is apples to oranges. The average yield of even a high yield savings account over the past 10 years is probably well under 2%, because interest rates and inflation were very low for a long time. You can't compare a 10 year average performance of a bond fund with the current savings account interest rate.
Also, the performance of a bond fund has very little to do with the yield of any specific bond. It also depends on price changes of the bonds, which depends on various market forces.
A bond fund spreads out the risk. A well managed fund will earn more money over time than a savings account. The trick is to find that well managed fund. If 2015-2021 were slow years for bond funds, look for the fund that made 3% instead of 2%.
