Insurance lowballed my totaled car by $6,000 - how do I fight this?

I am so frustrated right now. My car got totaled last week - someone ran a red light and hit me, 100% their fault. Their insurer accepted liability no problem. But then they sent me a total loss valuation and the number is $6,000 less than what comparable cars are going for in my area right now.

I drove a 2020 Honda CR-V with 38k miles, excellent condition, full service history, brand new tires put on 2 months ago. They're offering me $21,400. I literally see the same year/trim on CarGurus for $27,000-28,500 right now. This is insane.

Has anyone successfully challenged a total loss valuation? I dont even know where to start. Do I need a lawyer or can I do this myself? Also I'm paying $45/day for a rental out of pocket while this drags on which is making me want to scream.