Actually my point is that people thought Mt St Helen’s was safe too... much like they think that the volcano that Mexico City is on is safe.
Are they? Only hindsight gives us an immutable answer, the rest is probabilities and educated guesses.
Nobody can forsee the future or guarantee that all of the underlying assumptions are correct.
Current scientific theory on Earth age is based on assumptions that radioactive decay rates have remained relatively constant. Their observations tend to support this, as they have never been observed to be substantially variable.
The only YEC theories I have seen that attempt to account for the observed data on uranium decay posit that by some yet unexplained process what appears to be 4.5 billion years worth of uranium decay happened within the space of about a year during the Noachian flood, and happened without the ususal heat that would be associated with the decay. Otherwise the amount of heat that would be generated by that amount of decay in that time frame would have vaporized the Earth.