The disjunct made up of the three statements seems fairly solid and many of us have lowish priors for the first two disjuncts, and so assign a highish probability to the third disjunct.

The simulation argument makes many assumptions, like: "a non-simulated person and a simulated person have the same chance of subjective experienced existence" and also "we can actually count number of simulations meaningfully".

Which is really really problematic -- for example what's the difference between a single simulation double-checking every computation vs two simulations of the same thing? What's the difference between a simulation running on circuitry of 2nm width, vs two simulations running on circuitry of 1nm width each?

We don't really have a clue about how to count and compare probabilities of existence.