Some elements are indeed so abundant that they can be used without any worries, like carbon, iron, aluminum, calcium, sodium and more than a dozen others.
The elements with medium abundance, like lithium, are available in quantities that are many thousand times less than the abundant elements, so even if we should be able to use enough of them to cover all our needs, if such elements would constitute e.g. one percent or more of the average composition of all the things we have, then that would mean that it is likely that they are used in quantities that are too large to be sustainable.
The less abundant elements are available only in quantities that are many million times less than the abundant elements, so they should never be used without first making sure that it is impossible to substitute them.
Nowadays, a lot of people all over the world have to spend a lot of work with the search of more abundant substitutes for less abundant elements.
Much of this work could have been avoided if better choices had been made in the past. The reason why many bad choices have been possible is that the costs for most chemical elements that are included in a product are fake, they include only the smaller cost for mining, processing and transportation before the product is made, without adding the greater costs that would be needed for the recovery of the element from an end-of-life product and for repairing the environmental damage caused by its mining.
The payment of these extra costs has been pushed into the future, when someone else will have to pay them, instead of the users of the elements mined now.