The one big thing in my opinion that hastened the end of the game, not counting corporate in Seoul, was emphasizing instanced missions over zone events and miscellaneous street sweeping.
I understand, seeing the long queues in games like Everquest when a quest is within the world and it ends in a boss fight that spawns 5 minutes after it last got killed, how innovative the notion that everyone gets their own boss fight and don't have to wait for it to return was, combined with large mission bonuses and reduced debt from missions emptied the streets in a very short period of time.
Now I started playing at the end of August 2004 and the streets and skies were full of heroes, and suddenly, they weren't. You still saw them going between missions, around the trainers, around the tram stations, in the stores and Icon but it wasn't the same. Then they started to add QoL features that made it easier to travel to your missions, no longer needing to wait for a tram or transfer in Sky and Steel between the two. When they added the universities, The Vault and Wentworth's it was three more places you could find gatherings of heroes but eventually they too got QoL rewards and methods to let them do those activities elsewhere. Icon was the last local until trainers became tailors as well.
Some of this happened after the introduction of AE sort of as a way to provide some of the same convenience but in the normal game but the end result is you didn't have to transverse the city anymore. Travel powers at a low level makes some sense from a RPing PoV but it primarily meant the the city was fly, jump, port over or speed by country. At least back when we had to hoof it for 14 levels on the ground we felt like we were in a city full of people wandering the streets.
The end result was what looked to be an abandoned city, empty of heroes, instead of the city I first entered nearly 9 years ago. If you were a new player you would wonder if anybody else was playing. With private channels being the normal way to communicate, with hide being the default condition of players who played during the RMT invasion post market and maybe a third of the player population at peak, a new player would wonder how you can play an MMO without other players.
Notice I'm not really talking about difficulty in playing, just environmental changes over the years.
I've been playing GW2 for a while now (letting the boos die down) and one of the aspects I enjoy about it is every zone is full of what's called dynamic events. Think of the troll rave or apartment fire except multiply that by 20 in every zone. And with their philosophy that encouraging player cooperation being paramount, players can join in or leave without the need to join teams just so they get better rewards. There is no tagging of critters so they count toward your total and not someone else. Everyone gets the same XP and number of drops of loot as long as you do some minimum amount of damage. But most important is as these events occur, it causes players nearby to rush over and join in which means you see and meet other players all the time in the open world. And as they join in (well get within an range of the event) the event scales up and as they leave it scales down. It also helps that they have a daily reward if you do 5 of 9 variable goals for the day and event participation is almost guarantee to be one or more of those goals.
My point is it's not that the game got too easy from making the critters easier to defeat, it got easier for your character to not be a involved with the game world and that leads to a world where to an outsider, a new player, empty of other players and that's death to an MMO, the appearance that it's already dead.
