Serizawa's self-sacrifice indicts the category of weapon it deploys
Dr. Serizawa kills Godzilla with the Oxygen Destroyer, then kills himself — explicitly so the technology cannot be replicated by states. The film's resolution is an indictment of the very category of weapon it just used to win.
No Hollywood monster film of the period takes that turn. The standard shape is: threat appears, hero defeats threat, order restored. Gojira delivers the defeat and then destroys the means of victory, because the means of victory is as dangerous as the threat. Serizawa's death is not heroic sacrifice — it's preemptive arms control performed by a single scientist who doesn't trust institutions with what he knows.
This is what separates the 1954 film from everything the franchise becomes. Later entries solve Godzilla; the original refuses to solve him without paying the full cost of the solution. The moral weight isn't on whether Godzilla dies — it's on what it costs to kill something that shouldn't exist.
The franchise's later drift toward Godzilla-as-defender isn't a betrayal — it's what happens when popular culture turns its trauma figure into a recurring protagonist. The 1954 film works precisely because it hasn't yet figured out how to live with him. Anno's Shin Godzilla (2016) is interesting partly because it tries to recover that not-knowing.
Source claim: Serizawa's self-destruction with the Oxygen Destroyer is an indictment of the category of weapon it deploys — the film refuses to let the victory stand without destroying the means of achieving it.