I don't know because, frankly, your English might use some polish.
So I will try to ask you in different way ;)
You said:
I think the beginners should not be overwhelmed with all kinds of obscure grammatical forms,
so my question is: why in your opinion the form 'myśmy są' is more obscure then 'my jesteśmy' ?
Or why 'myśmy pisali' is more obscure then 'my pisaliśmy' ?
'jam pisał, jam pisała' = ' ja pisałem, ja pisałam'
'tyś pisał, tyś pisała' = ' ty pisałeś, ja pisałaś'
on the left side : jam, tyś, pisał, pisała = 4 new words
on the right side : ja, ty, pisałem, pisałam, pisałeś, pisałaś = 6 new words
What is more difficult to learn: 4 new wordds or 6 new words ?
What is more obscure for a beginner ??
Would you like to explain me ?
I'm not a language oriented person or teaching oriented.
I'm just really curious as for me more words and more rules was always more complicated and obscure especially when i was absolute beginner.