Opus 5 and Fable 5 were unbearable in their writing style. They were very cryptic and hard to understand.
Opus 5.5 is a massive improvement.
I really didn't like Opus 5 and was vocal about it. Opus 5.5 is noticeably better, but literally just yesterday I was fighting parsing some summary it had given me and it was a bit like the old days. IOW, it is better but still has some room to improve.
You can easily change its writing style: https://code.claude.com/docs/en/output-styles
You can also customize further by putting notes in your global MD.
Opus 5.5 went back to the old writing style a few days ago.