How old is too old to fight? There were historically some pretty old Roman generals who did fight on the battlefield, not to mention old knights who fought in the middle ages.
I can understand if a player prefers for their character to be extremely young, in their teens or twenties. If a player character was at least 20 when they began in Vanilla (year 25), then they would be at least 35 in Dragonflight (year 40), 5 years away from entering into middle-age. If you have played a second generation character that came into the story later on, like a Pandaren or an allied race, then the player character could still be extremely young, but ofcourse that character would have missed out on at least half of the story which would be incongruous with how the player character is treated in WoW (it makes little sense for a Wandering Pandaren who had no prior military experience when they joined one year ago to be handpicked by High King/Warchief as the leading general on Draenor in WoD).
Also this.
By this point, the player character should be one of the most famous people in the world, like the Warrior of Light from FF14 but 10x over given that the WoL saved multiple continents and worlds. He should be able to settle almost anywhere.
I'd like to imagine that my character retired to his farm at Halfhill in Pandaria. Maybe he shows up at the garrison every now and then (has someone has become the garrison commander? Am I an honorary commander now?).
Guess what.
Dragonflight is getting a book!
Maybe Blizzard should hire writers who can actually plan ahead and stick to the plan.
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I get the feeling that the stories of WoD and Shadowlands took place over a very short period of time, like maybe weeks to a few months at most. You and a handful of characters are going on a journey with a handful of objectives. You're not really burdened by logistics or the need to wait for your leaders to decide what to do next after a patch.
Most WoW expansions feel like they would have taken place over at least a couple of years. You have several different military campaigns that happen, and then more campaigns that happen in the patch content that would have had to have lots of time occur for the Horde/Alliance leadership to decide what to do next, military planners to get everything organized, asset buildup, logistics of intercontinental travel, and then the actual deployment. In Cata, there is no way that a Horde character could participate in the Stonetalon campaign AND the Barrens campaign AND Sylvanas' invasion of Gilneas AND Garrosh's invasion of the Twilight Highlands AND the Vash'jr campaign, AND the events at Mount Hyjal, let alone everything else that happened.