Honestly, if you actually have to ask why you ought be concerned about Michael Flynn, you probably oughtn't vote.
The reason we're in the mess we're in now--well, there's a lot of reasons--is that some 60-odd million people are too damn ignorant to be voting in the first place. Granted, some--perhaps a few hundred thousand--are adequately informed--they're simply bigoted, misogynistic, and, typically, quite wealthy sociopath who knew damn well that Trump would do their bidding, and fuck everyone else! But the rest are simply ignorant (though undoubtedly there's a lot of bigotry and misogyny there, as well): they don't understand or believe in climate change (funny how people who admittedly know so little often have such strong opinions about those topics); they deny white privilege and the long, and continuing, history of systemic oppression against the others--racial minorities, women, the disabled, non-cisgendered and so forth; and they believe that single payer healthcare will be incomprehensibly expensive, inefficient, and deny them of "choices" they believe they have now--again, all this belief without actually knowing a damn thing about it. This is kind of the height of irresponsibility as far as being an informed--and influential (as far as votes go)--citizen.
I personally do not consider myself all that well-informed about any and all matters political. I consider myself sufficiently informed so at to entitle me to vote--but only just so. Were I to be any less informed than I am now, I would feel quite irresponsible by exercising my right to vote.
In short, if you can't even get your basic facts straight about the basic issues, the histories, and the implications of policy decisions, you probably should not be voting.