More than 35 years after the discovery of non-conventional superconductivity in layered cuprates, a consistent picture of their special behavior is still missing despite the efforts deployed. Experimental observations and theoretical hypotheses have been accumulating over the years, with scant advances in terms of clear-cut simplifications. The reason for that is in the deep entwining of charge, spin and lattice degrees of freedom that govern cuprates. Resonant X-ray scattering (elastic and, mostly, inelastic, ie RIXS) is however providing observations helpful for the simplification of the picture. In fact, by RIXS the energy scale of orbital [1] and spin excitations [2] were definitely assessed, in parent compounds and in superconductors. More recently, RIXS revealed elusive charge order and associated fluctuations strongly mixed with some lattice modes [3]. Moreover, RIXS has eventually been used to detect the opening of the superconducting gap and of the pseudogap in YBCO [4]. And superconducting infinite-layer (IL) nickleates, the closest analogues of cuprates, are being studied with RIXS very successfully [5]. I will provide an overview of the recent results on cuprates and IL nickelates obtained by our group, with an outlook to the new opportunities available at XFELs.