It’s fine to express the gulf of evaluation and execution that led to the error. It happened. There may not be any better known solutions at the moment to lower the risk any further.
Calling them careless is also unjustified. They made a mental error processing the information. Whenever humans are involved there is a risk of illogical and bizarre mental errors in decision making because we are degenerating meat robots granted full agency.
Shit happens. How we emotionally deal with it is the test of life as a human being.