And my guess is that it's all Simon Belmont's fault.
Not in canon, mind, but rather, due to his status as an unlockable character in Boss Rush. Simon Belmont was restricted to his old 8-Bit NES sprite from 1987, and all the... gloriously limited movement that original Castlevania allowed him to have (though use of a Gameshark could add in Juste's movement upgrades with some hilariously stilted sprite frames).
But I surmise that this is the real reason that the Dracula fight in harmony of Dissonance was so weaksauce. They had to hamstring the boss and its AI so that it was possible to beat it with a self-crippled-by-comparison NES character without giving the NES character HP-wall levels of tankness.
In story, the weakness of Dracula is chalked up to it not really being fully Dracula, but rather just his reanimated remains (translated as "Wraith" in English but in fact closer in nature to that of a Revenant) being possessed by the cast-off Mister Hyde-esque side of Maxim's personality, which was in turn created by Maxim being possessed by echoes of Dracula's emotions haunting his former body parts. Because that's a lucid plot for the ages. In other words, the Revenant/Wraith is a weak Dracula fight because he's only... sort of but not quite actually Dracula. At least in story.
The real reason seems to be that they had to nerf him so a 15 year old gamesprite could whip his head off without cheating.
Just a revelation that I had.