I think a lot of the hate for the portal has to do with the fact that initial leveling was so slow, and required such a time investment, that a lot of people burned themselves out. Hell, I burned myself out. There is/was also the problem of difficulty scaling; I found myself doing a lot of Ops that were out of my depth, either because I was adding too many modifiers and cranking up the Delta, or because I was doing Fireteam Ops that were woefully over my head. So you've got the double whammy of not feeling very rewarding while also, often, feeling brutally hard. People (me) ended up running Solo Ops into oblivion because that's what we [i]could[/i] do, and those Solo Ops got old in a hurry. There's also the fact that it feels like Bungie was trying to replace the World; people liked going out to do quests, patrols, lost sectors, playing in the world, not just of the world. Now those open world activities are no longer rewarding, only the portal offers competitive rewards, and some people hated the change. I don't hate the Portal, but in its initial state I totally understand how people could. It's much better balanced today, after the reworks, but old frustrations still linger.