Is it a good idea to buy very long-maturity bonds?

Investors (in the United States and Europe) can be tempted to buy very long-maturity bonds to obtain an acceptable yield. But we believe this is a very bad idea. We believe financial markets underestimate future inflation in the long term, which may be quite high because of the presence of many structural causes of inflation (population ageing, rise in the lowest wages, return to regional value chains, energy transition). We therefore believe yield curves are now far too flat for very long maturities and that very long-term interest rates will rise significantly.