I have been blogging about DAX since before Power BI was a product; I started back in 2014 and Power BI was first released as generally available in mid 2015. Until about 2017, the only way you could build a commercially viable production reporting tool that used DAX was via Power Pivot. Unfortunately, as they years progressed, Power Pivot fell into a state of disrepair. It got to a point where I simply stopped using it because it was too unreliable. Read my articles here. https://exceleratorbi.com.au/?s=power+pivot+update
Today I read that Microsoft has announced a major update to Power Pivot for Excel. It is bringing 92 new DAX functions into Power Pivot for Excel. I hope that they also deliver improvements in the Measure writing UI (right click a table, add measure is terrible) and maybe also an update allowing bi-directional relationships – let’s wait and see. Personally, I would upgrade just to get access to SELECTEDVALUE( )!
If you are using Power Pivot for Excel, it might be time to ask the IT department to push through an update to your organisation.