Because "$X is bad" is boring, especially when it comes to LLMs. I use Opus 5 and it's fine. It's more chatty and sometimes a little more difficult to steer than 4.x was, but I've found the code quality of 5 to be much higher.

Everyone has different experiences with these things (for example, I've never experienced what you describe), and "$X is bad" is not conducive to thoughtful discussion.

The issue isn't whether it's fine, it's that both Fable 5 and Opus 5 are worse to use for the job of programming than Codex-5.6-Sol in my experience. I am directly comparing these top tier models every week in my work, and many friends have left Claude in favor of Codex recently because of Claude's poor model quality.

One thing I do like about Claude is that the normal (non-Code) chat interface supports MCP, whereas ChatGPT basically does not.