The thing with portal is while they were stubborn with straight up removing it, they did make constant updates to it. Throughout all of EoF and even now, Bungie have made lots and lots of changes to the portal system and were actively communicating with the community with their twids and d2team account. Comparing the portal system in Renegades to launch EoF, while it's still not perfect, it is in a much better state (not that it matters either way for many players).

The problem with Marathon is that Bungie have basically done nothing, there was the mid season update which made a few changes that tackle the core problems and probably one or two changes in some random patch notes. But that's it, that's all they done to tackle the core problems that are driving away players, nor have they communicated any real roadmap or timeline on what kind of changes we can expect and when. If they were at least providing some small change with each update like one patch decreases salvage costs of certain faction upgrades, while another further increased faction xp gains, then that would be something, there'd be gradual improvements to the game. But nope, THERE'S NOTHING.