It is not recommended to use the enumitem package with a beamer document class in TeX.
When trying without any further ado (just \usepackage{enumitem}) in a beamer document it will result in an error: ! TeX capacity exceeded, sorry [grouping levels=255].
The reason is that enumitem assums that the document class defines the \labelenumi command, but beamer doesn’t!
Manually defining it is not recommended: the beamer class (re-)defines the commands and environments, loading enumitem would then result in these being overwritten.
This stackoverflow answer provides a fix, but the generel consensus is to better not use enumitem if one doesn’t strictly need it.