My friends couldn't shuffle when we started either. When a deck would explode in a shuffling attempt, I would ask them "if they would like a bucket and a stick" to help mix the cards. It happened so often that the joke got tired. However, nobody gets a bye (unless physically unable, such as a arm in a sling).
Today all are very capable shufflers. Some even stick around after being felted to shuffle for the table. None are going to be casino dealers, and many still need help getting a card from the long end of the table to the other side, but all can shuffle.
It's not a complex task.
Well, it is if they are never taught. Teach them. Do yourself - and the poker world - a favor. The time you lose teaching them, will be won back quickly by shifting to a second deck.