Hot Take: Morgoth was Justified
Like the desire to create and be equal to your creator and being denied it is pretty tragic and I can see why he had his crash out
I'm aware that it's likely not possible for Eru to choose not to be all powerful but also he created Melkor and probably knew all this was going to happen and let it happen anyway.
A lot of this kind of boils similarly to the Satan vs God debate but I think this is different as it seems Melkor's initial view is sympathetic rather than coming out of nowhere
I am also aware this is not the intention of how it was written as generally Tolkien wanted everything to be black and white but of course nuances have found their way through