Commander Niall is a sort of sample platter of annoying fromsoft boss fight tropes: inescapable AoEs, nonsensical reach, bonus enemies, shoebox arena, annoying runback complete with enemies that hit you through the fog gate
The best I can say about Rykard is that he's 'less annoying than Bed of Chaos'. I think people mentally filed him under 'gimmick boss' and sort of disregarded his annoyingly long health bar, repetitive move set, and utterly nonsensical phase two attacks.