The equilibrium real rate depends on features such as the households’ propensity to save, and the central bank cannot influence this. The ECB did not lead to this environment with underlying negative real equilibrium rates. The ECB responded to the decline of the real equilibrium rate by reducing the policy rates, and consequently the real rates declined throughout the economy.
Had the policy rates been cut less aggressively, real income and inflation would have been even lower today. Now think about the implications for retirement saving by an average household, had the ECB reduced rates less aggressively. The real interest rate would have been higher, but the household’s income would have been lower.