So just a little question about Mordekaiser's Death Realm

Do you guys think it's fair that he can still hit the enemy nexus while he's in the Death Realm?

I just played a really close game as Mordekaiser where the enemy's Diana was absurdly fed and she could pretty much one shot any member of our team. Late in the game, the enemy team managed to get baron and push into our base, destroying all three of our inhibitors and almost killed both of our nexus turrets forcing us to defend until they respawned.

A while later we manage to force a fight in mid lane and the two most threatening people on the enemy team die (Diana and Kai'sa), and the only survivors on my team were me and Thresh. We rushed their open nexus but the enemy members that were still alive (Pyke, Zac and Poppy) collapsed on us, and they quickly killed Thresh as I ran to the nexus and started attacking it trying to end. At this point Diana and Kai'sa respawned, and the entire enemy team charged at me as I painfully slowly chipped away at their nexus.

However, before they could even do any damage to me or CC me, I was able to simply ult the enemy Pyke who couldn't really do that much to me because of how absurdly tanky I was and so the rest of the enemy team could only watch as their nexus slowly went down to 0 hp while I was hidden safely from harm in the Death Realm. I'm pretty sure that if I didn't have my ult there was no way in hell I could've ended there alone in a 1v5.

Anyway, do you guys think that it's fair that Morde is able to do this? Imagine how bullshit it must've felt for the enemy team when I was the only member of my team that was still alive and then I just suddenly disappeared from view with the weakest member of their team and they couldn't do anything to stop me from destroying the nexus and winning us the game.

I'm just curious to see what other people think about this interaction.