You might argue it’s not the same thing, but the effect is definitely the same: the law changed and people went from unchargeable to chargeable
What you’re arguing against is absurd. Regardless of the existence or lack thereof of a relevant statute of limitations, ex post facto laws have nothing to do with prosecution of acts that were already illegal at the time they were committed. It may not engender respect for the law or respect for lawmakers to remove the statute of limitations after the time has already passed, but I side with those who the law has already failed: victims of those who break the law to the detriment of victims.
If justice delayed is justice denied, then the statute of limitations is a double-edged sword that makes a mockery of the law and of those victims of the law’s failure to be enforced; the original victim is victimized again by denying them their just reward: justice itself.
Similarly, we collectively also suffer as a society when lawbreakers aren’t held responsible for their actions, which further foments contempt for the law, by allowing a state of affairs that is demonstrably unjust.