I'm inclined to agree with Legate's final conclusion. Fingolfin saw at the time that no matter what the Elves & allies did, final defeat was inevitable, so he set out to attempt the best he could. There are parallels with Finrod here (although Finrod's death did achieve something more), whereas in the case of Turgon, he decided to stay shut behind his hills.
If there's a moral here, it's probably "far better to have tried and failed".