Yeah this is one of those pieces of advice that probably works really well for NT people but not so well if you're autistic. Getting out of your comfort zone is important, but like... putting yourself in situations that are likely to trigger anxiety or meltdowns is only going to reinforce the idea that going out will cause anxiety and meltdowns.

They're not wrong about classical conditioning - it's just a completely different set of challenges when you're autistic. An NT person might go to a party and think, "huh, I guess that wasn't as bad as I thought it would be!" But for me, I will leave that experience feeling battered and exhausted from the sensory overload and social interaction. People like us need to start much, much smaller in order to expand our comfort zone rather than abandon it altogether.

Edit: but it is important work and we do need to put in the effort. Socializing is a necessary part of doing socialism.