How are you validating your content? (courses/newsletters/documentation)

We've all experienced buying courses or subscribing to newsletters only to feel let down by the actual content. It's just not good enough. I'm interested in learning how folks focused on quality content have validated their content and/or built more confidence in that:

• they're covering the right things (i.e. topics/sub-topics, etc.),
• their content comes across as intended (i.e. wording, formatting, etc.), and
• their readers/students find the content insightful, actionable, or inspirational (whatever you're going for)

With courses/newsletters there's a lot of focus on acquisition and monetization. There's much less talk on how to ensure one is putting out something people love to read or find especially useful. (Granted, everyone thinks their content is good).

I'm interested in hearing from those of you that have obsessed over the quality and the utility of what you put out.

What have you tried? What exists? What's good? What's doesn't work?

(Not looking for vanity metrics like views, open rates, CTR or similar...)