"Pseudoscience" isn't the only possible criticism of cryonics. One could believe that it may be scientifically possible in theory, still without thinking that it's a good idea to sign up for cryonics in the present day. (Basically, by coming up with something like a Drake equation for the chance of it working out positively for a current-day human, and then estimating the probability of the terms to be very low.)

You're right, that most of the popular criticism of cryonics is mere non-technical mocking. Still, there's a place for reasoned objections as well.