There are many factors that could be causing the slow extract. The network could be less performant than the one that was at your previous company. Try running the query directly against the datasource from the same computer. Does this have similar execution time? If it takes 3 hours as well we know the issue is not with Tableau Desktop.
Additionally, I would make sure you have upgraded to the latest release of Tableau Desktop 10.5.8 or upgrade to the latest version 2018.2
There could also be something limiting the connection on the data source side. I would verify with the DBA there is nothing limiting the connection.
Hope this helps!