Why is Ricardian Equivalence Important? Ricardian equivalence is a result regarding the ineffectiveness of government due to consumption smoothing behavior of consumers. A primary reason why it fails is due to population turnover (i.e people have finite lives).
In spite of these issues why is Ricardian equivalence important to know about in terms of its use as actionable information.
This link to a 43 page paper: Ricardian equivalence: an empirical application to the Portuguese economy CarlosFonseca Marinheiro
https://core.ac.uk/download/pdf/6978949.pdf
Introduction on page 3:

The fiscal policy may be used with a stabilising role if the government finance decisions are able to influence private consumption (i.e., aggregate demand) and saving. This influence depends on the degree to which consumers treat government debt as net wealth.

If Ricardian equivalence holds then the government cannot stimulate aggregate demand by increasing spending and/or reducing taxes. So history of economic debate over the effectiveness of fiscal policy includes this theory called Ricardian equivalence.

According  to  the  Keynesian  consensus  consumers  treat  government  debt  as  net  wealth. Therefore, a substitution of debt for taxes has a positive influence on private consumption and  aggregate  demand.  However,  the  consequent  decrease  in  private  and  national  saving, implies  an  increase  in  the  real  interest  rate,  which  crowds  out  private  investment.  The reduction  in  the  capital  accumulation  then  leads  to  a  reduction  of  the  long-term  growth prospects of the economy. This negative long-run effect offsets some of the positive short-term effects of the government deficit.


The  Ricardian  thesis  has  a  complete  opposite  view.  It  states  that,  for  a  given  expenditure path, substitution of debt for taxes has no effect on aggregate demand nor in interest rates.The  government’s  inter-temporal  budget  constraint  implies  that,  for  an  unaltered  level  of government outlays, a tax cut now implies a tax increase in the future. As borrowing only postpone  taxes  for  the  future,  consumers,  who  are  simultaneously  taxpayers,  anticipating the increase in future taxes, do not consider the current tax cut and the consequent increase in  disposable  income  as  being  permanent.  Their  inter-temporal  budget  restriction  is  left unaltered.  Therefore,  consumption  is  also  unaffected.  The  increased  disposable  income  is entirely saved.

Then there is another historic economic debate over the concept called &quot;crowding out.&quot;