Well, the story is much more than just that. It wasn't just simply about O2 and flammable mat'ls. A bunch more concerns and deficiencies were brought to light in the investigation that followed. It wasn't just that they had been going with what was done before without adequate questioning- the project, the capsule development, had been rushed. The hatch had been designed to open inward; this impeded access to the crew after the fire started. Probably just always the way they had done it- easier to engineer for inward opening as it naturally holds against pressurization. It was redesigned to open outward. Wiring throughout was described as a "rat's nest" and spoke to the issue of a short circuit. The death of crew forced a reckoning that gave permission to rethink and rework everything from a safety & reliability perspective. Even with the delays this entailed, they were still ready to go to the moon by late the next year and to complete the landing within the decade, per goal. It's considered likely that without the forced do-over initial moon missions might have failed, with both crew lost and goal missed as result.
Also it wasn't called Apollo I. Ground tests were not considered missions. No headlines of the time would have told about an "Apollo I" fire. The pad test was posthumously given that title by NASA so that the guys would have an actual mission to have died on.
