Indeed, the bomb dropped over Hiroshima was not of a tested design. In practice, an untested capability is still a capability. Having conducted half a dozen tests, India's nuclear scientists have declared there is no more need to test. The only ones who can feel really good about half a dozen tests are the scientists themselves over a difficult technical achievement. The rest of us can ponder over the incremental gains from the tests, if any.
Nuclear deterrence is unaffordable.
We should spend our scarce resources on economic development and social welfare. The argument that we should direct our limited resources toward more worthy objectives such as clean water, health and education for the underprivileged tends to be made uncritically. Besides, critics assume that a nuclear force will inevitably be a bloated and horrendously expensive one. The French and the British have small but deadly forces, and maybe even these are too big. A sensible nuclear force can be very small.