So, Jotunheim represents resistance to growth and stagnation. Freezing things in place, against all of the good things that come with innovation, resisting necessary and healthy change and growth. The ultimate in conservation for the sake of such, without allowing the sort of change that is necessary for life to prosper.
Muspelheim is change out of control, of chaotic change, of change for change’s sake, without consideration of the consequences. Change that may begin as growth but becomes destruction. Think of not only the changes we initiate (like clearcutting, or building communities where it’s dangerous to do so, or things like toxic waste being dumped in the environment), but also natural disasters like fires and floods and earthquakes out of our control.. Sudden, massive, uncontrollable change.
Just as the Hávamál often counsels moderation in our behavior, so too do we live in a moderate world, the LITERAL “Middle world”, Midgard. We can’t and shouldn’t resist change and growth,but we shouldn’t pursue it for its own sake without being aware of and able to deal with the consequences of change.
That’s why the giants - frost AND fire - are a problem and enemies of our Gods and Goddesses. Both forces seeking to engage in extremes that aren’t good for life on Earth. That’s why our deities oppose them both, and why sometimes, a giant might see the light and come join those of us in the middle path (I am specifically thinking of Skadi here). Both extremes are, ultimately, anti-life, as life can’t exist in stagnation or in uncontrolled chaotic destructive change.
Just a thought, and also my thought about how we, too, should seek that middle path away from both extremes.