This has made me genuinely very irritated. They take up so much space now! Why the f- do Mozilla insist upon making these fundamental but completely pointless c

This has made me genuinely very irritated. They take up so much space now! Why the f- do Mozilla insist upon making these fundamental but completely pointless changes? I have this software staring me in the face ALL the time, I don't need tab functionality being so large and distinct. I've not been bothered by a lot of UI changes as each update has allowed them to be reverted quite easily. It seems that every update has me swearing for 15 minutes until someone on HN helpfully points to a solution, but not this time. GRR.