MWI is just the unitary, deterministic, local, continuous, linear evolution of a partial differential equation. There's no extra semantics that need to be added to tell you how to interpret it.

It's the only interpretation of quantum mechanics that has all of these properties. Others fail most of those qualifications. I'm particularly bothered by the thought that we don't live in a deterministic universe. This is what I mean by "more elegant".

As for whether our universe is a simulation, I'm familiar with Bostrom's argument, which you outlined. It's certainly an interesting idea and might be correct, but orthogonal to the original question of interpretations of quantum mechanics.