The possible explanations for this delayed uptake are likely pragmatic: (i) many-body wave function-based quantum chemistry alternatives such as coupled-cluster or configuration interaction have widely been, and still are, considered the state-of-the-art , and (ii) existing GW -BSE implementations in solid-state codes with PBCs and a planewave basis are rather inefficient for isolated systems, requiring large and mostly empty unit cells. With implementations without PBCs and localized-orbital bases instead of plane-waves becoming available, several groups showed that Green's function methods are very powerful also in molecular systems, balancing -simplified speaking -the accuracy of more computationally expensive wave function methods with the cost of timedependent density-functional theory (TDDFT). One of the most notorious problems, for instance, of TDDFT is the very sensitive dependence of predicted charge-transfer type excitation energies on the choice of the exchange-correlation functional . In GW -BSE these excitation energies are predicted with the same accuracy as localized excitations (compared to the experiment) usually without the need for special tuning .