Are some lies not worse than others? When Trump says 1.5 million people attended his inauguration, that's a lie, but it's also mostly harmless and not worth prosecuting. When he says the election has been stolen, that's also a lie, but it led to an insurrection against the government and an attempt to overthrow democracy. The impact of the lie matters.
If propagating the lie that spurs a violent insurrection isn't impeachable, what is?
We spend billions of dollars a year in this country locking up people who have done far less. I think we can find room in the budget for an impeachment.