Most good writers don’t have good writing advice. They’re just good writers, so what they say gets wrapped up in something that seems like a good idea. All of this is make-believe
Courses, workshops, comped convention appearances where fans will take you out to dinner: all stronger and more reliable income streams for most writers than actually writing.
This isn't me saying don't listen to writing advice, it's me saying that if you like an author and they're selling writing advice, consider paying for it, because unless they're world famous or independently wealthy, they're probably broke as hell, and need your help.
This is a double warning to writers: how much time does the agent you're thinking of querying spend selling courses on how to query compared to how many books they actually sell to publishers?