Not understanding the lore doesn't make the game bad, it means you should read more. The Lords and Seath have lost much of their power over the centuries. They aren't the creatures we see fighting (murdering) the dragons in cinematic cutscene. They are diminished by Gwyn's actions. Quick rundown of what has happened to them:
Witch of Izalith: Turned into the Bed of Chaos, not by choice, but by freak accident. This malformed web of roots isn't something she would function well in as she used to be human-like.
Seath: Went mad from his obsession to find immortality and thereby mutated his subjects and himself into grotesque beings with haphazard limbs and features that weren't granted for their need or usefulness. Seath WAS a dragon, but he's from that when we meet him. He easily destroys us in his study, but our reaching his immorality crystal sends him into a frenzied phobia, blinded by fear, he flails at us wildly in desperate hope of not dying.
Nito: His strength is directly drawn from the dead and death, but Gwyn's Undead curse, perhaps on purpose, cut down Nito's power as humans afflicted with the curse do not die. For this reason, Nito would lose more and more power as less and less humans/creatures die in the world.
Gwyn: He linked the first flame, but doing so burnt him to crisp, down to the soul. If we fought him at his height, he'd simply whisk us away in a single blow of lightning.