I've called out the many faulty "science" from Berman Era star trek and even Roddenberry. I simply stated the cause of The Burn was underwhelming.
I think it's better than the possibility that it was caused by some sort of hostile alien race. People who were speculating regarding that annoyed me.
My preferred solution would be that we followed up on the global warming analogy from TNG, and discovered warp travel itself was damaging subspace. Maybe The Burn happened directly due to it, or some advanced alien race intervened to stop further damage which could destroy the galaxy.
Bonus points here because this would have resulted in Michael being proven wrong in her quest to 'solve" The Burn. There would have been no solution; it would have been for the best.