What's the hardest part about writing replies with AI?

I've been experimenting with an AI-powered reply assistant that helps generate responses for emails, chats, and customer conversations. One thing I've noticed is that writing a grammatically correct reply is easy, but making it sound natural is much harder.

Sometimes the response feels too formal. Other times it's too generic and doesn't match the tone of the conversation.

For those who use AI writing tools regularly:

• What's the biggest challenge you've faced?

• Do you always edit AI-generated replies before sending them?

• What makes an AI reply feel genuinely human instead of robotic?

I'm curious to know what others think because I believe reply quality depends as much on context and tone as it does on the AI model itself.