We have requirement to create report on two child objects with the same parent object as following : 
1- Contact : Parent Object  
2- Custom_Object1 : First child object (master detail relationship ) 
3- Custom_Object2 : Second child object  ( lookup relationship  )
We depended on the below article and used joined report to implement this requirement :
https://help.salesforce.com/s/articleView?id=000386778&type=1
The report returns 25,366 rows , 2000 are displayed on report screen, when we export the joined report to excel file to get all the rows, unfortunately , as you know , there is limit on export reports for joined report as following : 
Joined reports always export as Formatted Report. Joined report exports can include a maximum of 2000 rows. Additional rows are clipped :
https://help.salesforce.com/s/articleView?id=sf.reports_export.htm&type=5
There is idea to increase this limit for Joined reports :
https://ideas.salesforce.com/s/idea/a0B8W00000GdeDrUAJ/increase-the-export-limit-of-2000-rows-from-joined-reports
 
We can't modify the report filters to reduce the returned rows as these are business conditions to get the records for the whole fiscal year. Splitting the report into two or more reports also not acceptable idea for our business staff.
So i am thinking that Joined Report apprach will not work for our case. Another apprach is creating/repeating new formula/calculted fields on the parent or child objects. Aslo this apprach is not acceptable as it needs creating additional fields ( 20 new field ) just to display them on report. That will cause headache to the admin as it needs more fields management in the future.
When there are huge/large data from multiple objects , Report types, Joined Reports, and Calculated/Formula fields did not work , what are the alternative solutions? Can SOQL help us in this case? If so, how is it the form of SOQL query on the mentioned objects? 

Please help 
 
Thanks.