Yes, I get it. If you are perceived as an expert the emails don’t let up. And I totally agree with the annoyance of being made to look like a jerk for not responding when you are dealing with pressing stuff like a client deadline or a family illness that is demanding massive amounts of your time. The point about using public resources is very true as well. Someone else has had and will have your same question, or something pretty darn close. Post your inquiry in public and multiple people will benefit from your frustration. And indeed yes, there are randoms who think that open source should come with technical support free from financial cost or continued learning on their parts. Finally, it is annoying when people want to be spoon fed after you have laid out a buffet of resources on your website. I get it.
Still, a stock email, written once, with an apology for the impersonal response and a whole list of links usually does the trick.