[1] It's been saddening (is this a word?) me for over six years now. Safari's dev tools were best in class, and then they never really improved. The UI was updated once or twice, each time making the UX considerably worse. People may complain about how Apple doesn't care about pro market anymore, but the writing has been on the wall for some time now, and the first canary in the coal mine was Safari.
BTW. If you're interested, go to Develop -> Enter responsive mode. And then go Develop -> Show web inspector. Good luck working with the unzoomable screen. The first time I saw it, I had to go outside and walk for a bit.