“At the same time, I think we really need to understand the fact that we are living in a different era and animals are making use of what is available to them.”

They just adapt. If the supply of snail shells is declining - probably because of the pollution of their enviroment - those shells become scarce. When there are plastic garbage shells availiable, the hermit crabs will utilize them instead, since it probably is easier to obtain them. They serve the same purpose to them.

Since the lifespan of a wild hermit crab can reach up to 30 years, it probably will effect their health. When plastic disintegrates and becomes micro- or nanoplastic, those particles will cumulate in their bodies. These plastic particles are suspected of being silmilar to hormones, which can have effects on the ability to reproduce, among others.

It should be rather concerning than cute.