Asisreo
Patron Badass
There's nothing radical about portals. This is a staple D&D encounter.If the DM needs to radically reconsider the interconnectedness of the planes for their game based on which classes are at the table, that essentially makes the opposite point of the one you were arguing.
The book puts portals as the number one way for interplanar travels to even take place.
Portals are an entryway, a door. Putting a portal in your overworld at some point is the high level equivalent of putting a door in a room in your dungeon. Even if its locked, secret, hard-to-find, or barred; there's still the expectation that if you need to get in a room, the DM would have put a door there.