As a teenager I always chased those infinite head rushes, thinking about essence/existence/eternity, etc!

I remember specifically in 1996, at 16 years old, driving to work on 141, while contemplating the exponential growth of video game verisimilitude and independently arriving at simulation theory. A pretty common occurrence presumably!

The idea never really went anywhere though, for reasons very similar to what you've eloquently elucidated here, as evidenced below :)))

In order to function as an object of experience reality requires simulation on the individual level anyway, so whether the exterior data source originates organically or synthetically, we still only have our own reality tunnels as a reference frame.

Unless the simulated substrate has unique and knowable interface opportunities and/or limitations, it doesn't really amount to a fish big enough to fry, in my estimation!

My instant and lasting reaction to simulation theory remains: "If so, so what?"

Not necessarily in a dismissive way! But just that I've already accepted the non-impossibility of the premise, and that alone doesn't seem any more impactful than other formulations of impermanence and uncertainty.

A simulation theory with testable implications on our living conditions would interest me.

Otherwise, it mostly seems like noise best left to blow the minds of teenagers on their way to bigger and better ideas!