Most problems related to xml import, whether in wordpress or any other application (php or not), are more related to server performance.
Often people encounter errors related to timeout to load the file. It may also be that problems are encountered when loading a very large database in xml, and it even hangs. A way out of this situation is split the xml in multiple files - it may be for period, for example, making an xml for each year of website content. Most of the time it works.
I, particularly, prefer to import data by database. The advantage of xml is that it can import media files directly from the old site if the urls still work.
About the plugin, if you are talking about the WP Importer (https://wordpress.org/plugins/wordpress-importer/changelog/), it was last updated in October 2014.
An option to this first plugin is the Advanced Importer (https://wordpress.org/plugins/wp-advanced-importer) - never tested, but has great recommendations. maybe can be useful to you. Your last update was this month.