Slow speed on gravel bike. Advice?

I bought a gen 3 Checkpoint a month or so ago and it came with Bontrager Girona tires (pretty much last on the list at www.bicyclerollingresistance.com) and ridiculously wide 46cm bars. I swapped the bars immediately and tires after a few rides and noticed a nice boost in speed.

Fitness and bike fit are going to have a huge impact of course, but you can get a nice boost with good tires right away.