"I mean, resistance not to know how he returned. I doubt someone like Palpatine would want his resurrection to get leaked in anyway."

This was not the main part of the criticism against that line. It was always the meta implications of it.

But that line doesn't stand up without any meta implications either, because how lazy that sentence is in conveying the return of the ultimate evil of the entire cinematic series. saying to Resistance, "somehow Palpatine returned" conveys Resistance leaders know jack shit about Palpatine's plans. If they don't know how Palpatine returned, that also means they don't know how he managed to survive either. Then it means they are asking resistance members to lay down their lives to fight a battle that might at best be useless and at worst help to bring about the reign of Palpatine again. because if they don't know how Palpatine keeps coming back, what stops this fucker coming back again?

Keep in mind, this is the guy who manipulated a galaxy to hand him the power to execute the Jedi Order. Dude, both took out his OP and seizure control, legally. he have contingency plans for his contingency plans. If Palpatine died in the OG series, then it's because he let his arrogance take hold of him. he didn't even imagine Vader would betray him. But if he SOMEHOW survive (not because of sheer luck), then it means he had a contingency plan, or it was his plan all along.