It's beind downvoted because "but, her emails..." is not saying it's the same thing, but rather, that so much fuss was made about her emails, and then when something similar happens, the right conveniently ignores it. For example, as you mentioned, signalgate, or the times members of the Trump administration used their "own email server and using it for official government communications and having your own personal email address used for personal communications."

It's being down voted because it's attacking a strawman. No one is saying they are the same exact thing. It's that you will see people activatley defending this as a big nothingburger when in truth, it's still a security breach that has the potential to lower our defenses.