For the GFC, there is for example the Stock/Watson paper (https://www.brookings.edu/bpea-articles/disentangling-the-channels-of-the-2007-2009-recession/) arguing that there was no structural break, just a bigger shocks. It is hard to argue the same for the COVID19-period. Also, the current GDP drop is bigger and faster than previous ones. With normally distributed shocks, this should pretty much never happen. Thus, these outliers will massively affect estimation.