They cast with a backwards offset (start offset was set to 0, persisted with higher offset as well)
They have arbitrary performance constraints (100 Niagara systems with 1 particle each will cause shadow projection/depths cost to skyrocket compared to 1 Niagara system with 100 particles in it which has negligible cost)
It’d be sweet to give them the love they need to get them up to speed with the rest of UE5’s graphical standards