What Sims does is make you defend the entire field.
He can run, so you have to defend outside the tackles, and between the tackles. You have to make a DB or LB account for Sims, so in a way you take one less defender out of 100% focus on every play Sims is in. He's fast enough to run by LBs and DBs, so can absolutely wreck the best defensive call.
Sims can throw to all 3 levels of the field (short, intermediate, deep), and he can do it with ease (see the Adonicas winning TD against Duke). What I liked about that throw was Sims threw Adonicas Sanders open...that is, he threw it where only Sanders could get it, all while a pass rush was barreling down on him.
So far, he's improved his completion % almost 8 points (55% in 2020 to 62.5% this season). Against UNC and Pitt, his completion percentage was OVER 70%.
Sims is growing as a QB before our eyes. The same criticism everyone is giving Sims, I heard the same things about Joe Hamilton early in his career. Right now, Sims is producing at modestly higher pace than what Joe Hamilton did at the same point in their careers.
If you want to worry about something, worry about our OLine and our defense. QB is further down the list of things we need to worry about.