The problem with Fire and Brimstone is that it causes the student to contemplate what is beyond this world.
The Gemara in Chagiga warns against doing so.
4 great Torah Scholars in the time of the Mishnah did enter “beyond the curtain”.
One committed suicide, one went crazy, one became a heretic and one emerged unscathed (Rabbi Akiba).
25% success and 75% failure rates.
Not every mussar sefer is appropriate for general audiences.
There are plenty other ways to teach accountability and fear of sin without Fire and Brimstone.
The sections of Rebuke in the Torah focus on consequences in this world.
Dante was the biggest advocate of lecturing Fire and Brimstone to the masses.