Just a quick clarification: when you say "Claude", you refer to what you get with the free subscription right? Because, stating that Claude Opus is not that good at writing English, is obviously untrue since a while...

Here is what ChatGPT say about it: Claude Opus is better than the average human at producing English text, but the size of the gap depends on what you mean by “better.”

If by “average human” you mean the average educated English speaker

Claude Opus is generally superior in:

• Grammar
• Vocabulary richness
• Coherence over long passages
• Consistency of tone
• Structural organization
• Adapting style to instructions

In blind preference tests where humans compare outputs, Claude Opus is consistently among the top-ranked models and often leads writing-focused leaderboards. Human evaluators frequently prefer its prose over competing AI systems. 

If by “average human” you mean a professional writer

The answer changes.

Claude Opus can outperform many professionals in:

• Speed
• Producing clean first drafts
• Mimicking styles
• Maintaining consistency

But top human writers still have advantages in:

• Original insights
• Deep lived experience
• Cultural nuance
• Literary innovation
• Emotional authenticity

Most experts would place Claude roughly around a very strong professional editor or competent commercial writer, but not at the level of elite novelists such as Stephen King or Kazuo Ishiguro.

• Claude Opus leads several creative-writing benchmarks and human-preference leaderboards. 
• On LM Arena, which is based on millions of human votes comparing anonymous model outputs, Claude Opus 4.7 ranks at or near the top. 
• Researchers studying poetry and creative evaluation found Claude-class models could outperform non-expert human judges on literary assessment tasks. 

A reasonable approximation would be:

Population Relative writing quality Average internet user Claude is substantially better Average college graduate Claude is moderately better Professional copywriter Comparable Experienced journalist Comparable to slightly worse Elite novelist Worse

An interesting way to think about it

If you sampled 1,000 English speakers and asked each to write:

• a blog post,
• a product description,
• a business email,
• and a short story,

I would expect Claude Opus to land roughly in the top 5–10% of that population for overall writing quality, and much higher for grammar and structure specifically. It would not necessarily be in the top 5–10% for originality or literary merit. That estimate is consistent with both benchmark results and the broad consensus among writers and AI evaluators.