All three are true: Bad tackling + Undisciplined football + Slow (especially when it came to reacting)
I’m glad you included the last point about reacting.
Too many people confuse being fast with playing fast. Often the players who seem the fastest are the ones who have accurately diagnosed a play and arrive a step sooner than someone who did not; sometimes arriving even before a “faster”player.
As an example, other than the Fields catch at the end of the PSU-UM game in 1999, I don’t recall Ed Reed ever not catch a player. Reed always arrived in time, if not early, and made the play. Reed was fast but he was nowhere near the fastest DB on the UM team, and that was even more true in the NFL. But Reed understand pre-snap what was likely to occur, and his reaction time once a play began was as elite.
Maybe we were a traditionally slow team last year on defense, but I agree that we were slow to react and that comes back to coaching and preparation. Even James Williams (I know true freshman) was late more than once. James certainly is not slow, but he was late. Once our coaching has our team prepared, we will be pleasantly surprised at how much faster we appear.