We don't really need multiple exits in case of fire because fires are occurring less often and people are getting plenty of warning.

I think this is much to broad.

Even the film does not suggest eliminating multiple exits; rather, it points out that it took a long time to replace external fire escapes with better alternatives. Specifically, internal, fireproof staircases that offer greater protection and are used regularly and therefore familiar to those fleeing.

When the redundancy is gone (not available, blocked, insufficient spaced) this can quickly lead to a disaster. Here are some recent examples

[1] https://en.wikipedia.org/wiki/2026_Crans-Montana_bar_fire

[2] https://en.wikipedia.org/wiki/Kiss_nightclub_fire

[3] https://gpe.wikipedia.org/wiki/2023_Johannesburg_building_fi...