Lemme explain why I said what I did hommie
- madara has 3 rinnegans, a rinnesharingan (kaguya's eye) and two normal rinnegans, I'm pretty sure he can use the portal cuz he has kaguya's eye which is capable of such a feat, only reason is, he had it for just a chapter
- madara has the chakra to use it (juubi jin) likewise hagz with his undivided chakra.
- madara was'nt trapped in a dimension so he did'nt need to use it (even sasuke could'nt use it till he later trained with his eyes in the beginning).
- and I for one think opening portals is a rinnegan feat, cuz kaguya, momoshi, and sasuke all have this feat, neither hagormo nor madara were in a situation that they needed to use a portal.
- if you say hagz should have used it to retrieve the bijuus and team 7, I'll counter with what he said, 'he does'nt have chakra' (cuz he gave naruto and sasuke ofcourse) and that summoning the dead does'nt seem to cost chakra as much as making a portal (a portal that'll fit a whole bijuu, and 9 of them + team 7), even sasuke can only do as much, so summing them is the wiser decision that costs less chakra.
- hagormo has complete control and mastery over rinnegan
- I think non jj madara (hypothetical DRSM madara), with training like sasuke, can achieve the portal technique
- and last but not least, its a rinnegan only technique (that's why I think madara can achieve this feat) why? Cuz momoshiki did'nt have a tomoe rinnegan.
Hope you get it