I mean, Simon’s moves and traits are almost all based on the original NES game and imo his moveset is fantastic (aside from his terrible recovery).
But I guess people tend to expect a bit more complexity from a DLC newcomer’s moveset.
Technically speaking.
Moves from the NES Castlevania:
-Cross
-Axe
-Holy Water
-Non Angled Foward and Back Aerial
-Foward Tilt.
-Non-Angled Foward Smash.
Moves from Super Castlevania 4:
-Diagonal Angled Foward and Back Aerials
-Up Smash
-Up Aerial
-Diagonally Upwards and Downwards Foward Smash.
-Whip Twirl.
-Crawling.
-Tether Recovery (which is based on Simon's ability of holding onto floating rings that allow him to swing across the stage in SC4)
Castlevania Harmony of Despair:
-Down Aerial which is a foot dive (it's actually standard in MetroidVania games of the CV series, but neither Simon nor Richter could do it until Harmony of Despair)
Moves from Richter in Symphony of the Night:
-Up Special: Uppercut (which ironically was used for reaching high altitudes in Symphony of the Night)
-Down Tilt.
-Dash Attack.
-Grand Cross (although nowadays that ability seems to have been rectcon'd to be used by all Belmonts, like Trevor in Curse of Darkness and Simon in Judgement)
Made up for Smash:
-Infinite Jab
-Neutral Aerial (although it resembles Nathan Graves's Whip Spinning ability from Circle of the Moon)
-Grab, Pummel and Throws.
-Floor Attack and Ledge attack.
So while Simon clearly is mostly based on the NES Castlevania games due to his aesthetic design (NES sound effects when hitting an opponent his hurt and lying stance clearly biegn based on CV1) his moveset actually includes a lot of references outside of CV1.
I can see Ryu Hayabusa clearly using his stance and sound effects from the NES game, and also using moves like his Ninjutsu Sub Weapons for Specials, the Wall Crawling, his standard sword Slash for a foward tilt or neutral attack, and his jump spin sub weapon as a Neutral Aerial, but im pretty sure they will use moves from Ryu's other non-NES games.