The limitations of using fossil in evolution theory are that fossils are rare and only show changes in bones of animals. In many environments the preservation of fossils is hard creating gaps in fossil records that can make identifying change very hard. And when changes present themselves they can be in many forms, such as changing in the soft tissue, coverage and thickness of hair, and changes in organs, all of which can not be preserved by fossilization.
I’m not sure what kind of answer you need but I hope this is sufficient. Hope this helps. Stay healthy and stay safe! :)