Atheists are unserious, but then so are Christians and so am I.
Face it: Human beings are not serious - or, at least, not for long and never consistently.
Therefore we should not treat people as if they were serious.
Our explanations are never serious - not wholly; and we always allow ourselves wiggle room somewhere (even if we hope that nobody notices; not even ourselves).
But this is not a gotcha.
When we are trying to get something right, we simply must keep it simple.
We must make sure the main things are clear and coherent - because, in the end, that is all we can do.
(And lucky if we do that.)
The alternative is to let things get complex, and inevitably this will mess up the main things.
Complexity = errors about big things (because of our inability to get serious and stay serious)..