First things first, there is likely a dual rate knob on your controller which controls the speed of the steering servo. Is it turned all the way up?
If so, it's hard to say since Spektrum RTR (ready to run) replacement servo specs are completely top secret, even to Spektrum customer service (I tried asking once)

Maybe it is just a slow ass servo? Maybe you got a dud

Is it the same model servo you had originally?
My advice would be to get a refund, since the specs are obviously so sh!tty they are ashamed to share them with their customers. The pic shows all the "product details" LOL. Absolutely no info anywhere to be found on it.
Horizon will want to see a video of it rotating. So pull it from the car and remove everything attached to it. Press the servo horn back on (no screw) and make a video of it rotating while waiting for a response from customer service. Record the transmitter knobs as well to show you have everything set properly. They may want to see how much toilet paper you have left in your bathroom as well
They usually respond within 24 hours. They will likely want to send you a replacement. I would argue for a refund, but accept a replacement if that is the only option. If they do offer a refund, never ever buy another Spektrum brand anything ever, ever, ever again
Actually, some of their stuff is probably ok

But you're better off buying cheap Amazon servos than Spektrum. Better brand names are Savox, Hitec, Tekin, Reedy, etc.