Making plans and running back of the envelope calculations is easy and fun; businesses actually require violent execution. I spent almost 10 years doing an objectively easier business. I wrote a million words about it, including substantially all of the non-obvious secret sauce about e.g. our SEO strategy. I got a variant of your comment more than monthly: the competitors are coming, the competitors are coming! And the competitors did, in fact, come... with C grade execution that had minimal impact on me.

I will note that the conversion rate between "I will totes clone your business in a weekend" and actually cloning the business was far, far below 1%.