I wasn't thrilled either. Granted, I don't see why they need a fifth season at all, but the episodes have been largely fillers, the writing IMO has been substandard and there's just too much extraneous nonsense that nobody actually cares about. Seriously, who gives a damn about the kid? They could have finished the whole thing up in 8 if they weren't still playing the obnoxious "will they or won't they" games with Decker and Lucifer.
Plus, who knows when the last 8 will air? By the time they do, will I remember what's happened so far or care?