How to make range parameter to dynamically use current date?

That's not how incremental refresh works.  The values for RangeStart and RangeEnd in Power Query have absolutely no correlation to the partition rules created in the Power BI interface for your table  (say, keep last 5 years and refresh last two months). These values in Power Query can be anything and are usually used to give the report developer just enough data to work with the visuals etc (for example when you need to do a Year over Year calculation).

There is a special case when the RangeStart is in the future but you still need to fill the partition. That is handled via XMLA script.