Licht's resurrection is pure Plotanium. There is literally nothing or no-one he cannot resurrect if the Plot calls for it.
The only limit i can see, and the "explanation" for the remaining dead is that those souls already willingly "passed on" and either reincarnated, Isekaied, or went on to whatever Eternal Reward they believed in.
Which in and of itself is a classic principle within the resurrection trope: you cannot resurrect someone "as a Good Guy™" if the soul is unwilling. ( Necromancy/Dark Magic is quite another matter...)