Most religions have warnings to the net effect of “the disbelievers are trying to get you to abandon your faith, but if you do, the Merciful God will throw you in Hell, so don’t even consider it!”.
Now if these religions are not all “true” in their current form, then picking one religion’s warnings means that you are ignoring (at least in part) the warnings of other religions.
So heeding the warning of the Qur’an means you are rejecting the warning of the Bible about not accepting Jesus as your savior.
I’m suggesting to the religious: you are more likely to heed the warning of your birth religion and rationally reject other such similar warnings found in the texts of other religions.
The fact that the Qur’an has such a warning does nothing to advance and encourage you to engage with it on a rational basis.
It does nothing to encourage you to consider, hypothetically, what if this isn’t true? How might I go about discovering that? The Qur’an doesn’t even acknowledge that a person could be sincere in their rejection of Islam. It paints a picture of every single ex-Muslim as necessarily disingenuous.
That characterization is itself, quite disingenuous of the author of the Qur’an.