Is that so?
Let us look at this logically then.
One principle of MMORPG design – and by extension WoW’s design – is that rewards are yielded appropriate to the time and effort invested.
This design principle is typically expressed in this manner:
Time + Effort = Reward
So what are some examples of that in WoW?
A World Quest to kill an Elite mob will yield a greater reward than a similar World Quest to kill a non-Elite mob.
That is because the effort needed to kill an Elite mob is greater, so the reward is appropriately higher.
If you play with Warmode on you get +x% extra rewards and experience. Why? Because the time and effort spent having to fend off enemy players in order to complete various quests is higher than not having to fend off enemy players.
This is the design principle that Blizzard balances rewards around in the game.
So how does this apply to portals?
Well, if you can complete an old instance without much effort or time spent, but still acquire a lot of gold and other useful items, then the balance of time + effort = reward is out of whack.
In the past Blizzard did a major pass on old content, effectively reducing the amount of gold and trash loot it yielded, because farming old content had become the predominant way of getting rich in the game. So Blizzard had to nerf the value of running old content, because otherwise it invalidated the time and effort spent on doing any of the current-expansion content.
The underlying problem is that the rewards in an instance like Karazhan are balanced around the effort it requires to complete the instance – which is trivial if you’re a max-level player – and the time it takes to run through the instance AND the time it takes to travel to the instance.
But if you have a portal right in front of Karazhan, then the time investment becomes as trivial as the effort required, meaning that you’re getting an overproportioned amount of rewards relative to the time and effort invested.
Let’s take a World Quest in Stormsong Valley, one of those where you have to kill a named mob up in the snowy mountains who’s trying to steal the precious Azerite.
That World Quest can reward upwards of 100g or 350 Azerite Power. Yet the effort required to kill 1 mob is trivial, easy and quickly done. So how can this World Quest be so rewarding? Well the answer is that the reward accounts for the travel time to get there in the first place. It takes several minutes from the nearest flight point and to the top of those mountains – and it is that time investment the reward is balanced around.
So returning to the design principle of Time + Effort = Reward, then this is really difficult to apply to old content.
The faster means of travel players get (flying, portals, etc.) and the more trivial the content gets (out-level, out-gear, etc.) the more rewarding the old content becomes. You simply get more bang for the buck, so to speak.
But that undermines all the current-expansion content where the time investment and effort required to complete anything is usually much higher.
That forces Blizzard to balance the rewards for completing old content relative to current-expansion content. And there are two ways of doing this. You can either nerf the rewards outright (which they have done once in the past already), or you can increase the time and effort required, so it corresponds better to the rewards given.
So from a logical perspective, if we say the guiding design principle for gaining Honor ranks or PvP rating or Mythic mode raid kills is that Time + Effort = Reward, then logically that same design principle should hold true to all other content as well – including old dungeons and raids. The rewards should correspond to the time and effort invested.
Are old dungeons and raids a rewarding form of content in the game? Yes.
Has the difficulty and challenge of old dungeons and raids decreased over time? Yes.
Have the means of fast travel outside and inside old dungeons and raids increased over time? Yes.
So is the reward overproportioned relative to the time and effort invested? Yes.
Are Blizzard in the right to seek a better balance by increasing the time investment through longer travel distances? Yes.
There is nothing illogical about this. You can dislike and disagree with it, but logically Blizzard’s case is sound.