TL;DR - WoD had a lot of issues, and while garrisons weren’t all that bad, a lack of content saw folks staying in their garrisons and feeling craptastic about the state of the game.
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“All you do is sit in your garrison all day” was a common complaint back in the day. The problem is less that Garrisons were the issue and more that WoD had no content in the world, which is a VERY big component for the game feel that Draenor just didn’t have at all.
Draenor had so little to do in the world outside your garrison that outside of the quests you’d do to get from 90 to 100, once you hit the level cap, you were done. The only thing that would really put you in the world was an apexis daily you’d get as the one daily quest available, where you’d go to a zone, kill things to fill a bar, and you were finished. And this was right after Pandaria, which had LOADS of quests you could repeat from NPCs that had a variety of different quests, dialogues, objectives, all of which gave the world more personality. All Warlords had instead of this were one-time collectables treasures.
Ashran just wasn’t really all that great. There were a couple of fun events, but on release, some servers had it be absolutely unplayable with how some servers handled faction balancing, so for awhile some servers just had the enemy faction farming their gate and pushing back towards your own base.
Arguably it was decent if all you wanted to do was raidlog. Hot take: BRF wasn’t that great. There were a few amazing fights that felt way more dynamic, but the rest was just kind of ‘eh’. It felt better after Highmaul. HFC was pretty fun at least, and having the unique class trinkets at the end was neat, but no matter how good the raiding was, nothing can save you from a lack of other content.
6.1 was the biggest embarrassment of a patch Blizzard has ever put out. Ever. The Selfie Patch will never be lived down.
Tanaan jungle was a step in the right direction, but it was too little too late. It was a MAJOR step down from Pandaria, where every patch added a new set of activities to do in a region with Landfall, then the Thundering Isle in 5.2, the Battles of the Barrens in 5.3, and of course, 5.4’s Timeless Isle. There was SO much stuff.
And then WoD happened and we had nothing in the world. There was virtually no incentive or reason to go out into the world, so people didn’t bother. Folks got used to lingering in their garrisons real fast.
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Real talk? As much as people don’t like BfA and Shadowlands, I felt leagues better with those games than I did with WoD. SL may have made me facepalm hard and the final patch of BfA may have made me groan with how the corruption grind went, but I’ll take those over WoD any day.