It is not a non-sequitor, it follows from the concepts, something being worth doing is not a part of physics/math. If math/physics is all you have then you have no "worth doing".

If it turns out we're just simulated entities, does that suddenly make your life not worth living?

Why would it change anything?

if we are simulated entities then there is no "we". 'we' do not have existence. that would indeed make life not worth living, on account of there not being a life there in the first place

If we are simulated entities, then the fact that I at least live a pleasant life would show that it is perfectly possible to have a pleasant, worthwhile simulated life.

no it would show that you are not simulated

It might, if it turns out there's an opportunity for a reset.