On the other end of the scale, there is "disinformation". That's where someone is deliberately and systematically trying to persuade you do believe what is false, in order for them to carry out their agenda. Russia has been running a disinformation campaign against the US for several years. (On both sides - trying to drive extremism and destroy the political center, in order to weaken the US.) One could say that both major political parties in the US are also running disinformation campaigns.
"Misinformation" is kind of in the middle, in my view. It's not necessarily part of a large-scale organized campaign, but it's not just a nonsense belief with no consequences. So people care about misinformation in a way that they don't care about the flat earthers, because misinformation can cause more harm.
But people don't seem to take as seriously as they should the damage that long-running, coordinated disinformation campaigns can cause (and, in fact, are causing).