You seem to understand the basic throw combo, and to vary it by opponent DI, which is good. Also, you seem to understand the power of Neutral-B.
The biggest problem I saw was a lack of understanding (or at least application thereof) of your special move options. You never used Up-B to kill (you had several opportunities around the middle of the video, most notably at 1:48 where you have Lucina stunned, but go for a non-fatal F-Smash instead). You only tried to use Down-B once (2:08) rather than regularly. You never used Side-B to recover. As I said, your use of Neutral-B was fine, keep that up.
Otherwise, you are dashing in too much. Neutral-B and Neutral-Air are safer ways to approach that don't leave you open for a shield grab. Do it from time to time, especially after they've done a laggy move, but not that often.
Also, while not a big deal on Omega stages, try not to use Down-Air too much. Even on Omega stages it leaves you open to punish if they shield, and on non-Omega stages (which is the majority of stages played in tournament settings, especially if you are ZSS, as she does well in the air with platforms) it's easy to kill yourself with a Down-Air.