HP Disc does not go full screen. It must eat a fireball to go full-screen, something it cannot do against an arching fireball zoner, which is both zoners currently in the game. So if you're dashing in, both Sim & FANG have escape options they can do against Necalli if he tries to fully dash in against their fireballs. Disc still has all the disadvantages of being a command input move, something it originally was, and gained no benefit from being changed to a charge input. Does Bison have to worry about throwing out scissor kicks? Does fang have to worry about throwing out the LP version of his double-hit bf charge move? No. But Necalli does. All of the disadvantages of a command input move, with no benefit of it being a charge technique that other charges in the very same game get to enjoy.
cr.hp is better as an anti-air? even though it doesn't actually gain any actual height for its hit-box when compared to other moves of Necalli that are actual AA, like his standing jab? The only opponents it would hit is someone who is aiming to land directly in front of necalli on a jump arc, which could also be hit by any of the other normals Necalli has.
You're right that getting in isn't what footsies are about, but Necalli HAS to get in because his normals do not have much range outside of two, cr.mk & st.hk, and both have more startup than most other respective pokes, especially cr.mk. Not only that, most characters can get some solid damage off their pokes in footsies, or they can convert pokes into solid mixups. Necalli can't. Necalli's optimal range is at near close - most of his hit confirms at that range lead to full damage, thanks to the opponent not being fully pushed out of his follow-up range once hits land.
Learn better spacing then. Honestly, there's not much more to say than what's already been said, you just sound like you're struggling with Necalli and are trying to find ways to blame the character.