SObjectHelper.cls

public with sharing class SObjectHelper {
    
    public static Object getRelatedFieldValue(sObject obj, String fieldName) {
        
        if(fieldName.contains('.')){
            String relation = fieldName.substringBefore('.');
            String relatedField = fieldName.substringAfter('.');
            return SObjectHelper.getRelatedFieldValue((sObject)obj.getSObject(relation), relatedField);
        } else {
            return obj.get(fieldName);
        }
    }
}