Earlier quoted context omitted.
The locked door is a ridiculous analogy when it comes to the open web. Pretty much all "door" analogies are flawed, but sure let's imagine your web server has a door. If you want to actually lock the door, you're more than welcome to put an authentication gate around your content. A web server that accepts a GET request and replies 2xx is distinctly NOT "locked" in any way.
Any analogy is flawed and you can kill most analogies very fast. They are meant to illustrate a point hopefully efficiently, not to be mathematically true. They are not to everyone's taste, me included in most cases. They are mostly fine as long as they are not used to make a point, but only to illustrate it. I agree with this criticism of this analogy, I actually had this flaw in mind from the start. There are other…
It is inherently a cat and mouse game that you CHOOSE to play. Either implement throttling for clients that consume too much resources for your server / require auth / captcha / javascript / whatever whenever the client is using too much resources. if the client still chooses to go through the hoops you implemented then I don't see any issue. If u still have an issue then implement more hoops until you're satisfied.