Of course its like that. And I realize the idea that content creation is sort of a zero-sum game is what keeps the envy alive, and the jealousy of "they made something I dont like, so it automatically took away from something I do like", but not all content is born equal.
A player who doesnt consider savage content, or extremes, to be content for them is the most likely to cry for less of that. There are quite a few of those around. But these people farm stuff, play around with housing etc., its not the same kind of ressources these things eat up, at all. I worked in the industry for 6 years, but even to someout outside of it there is plenty of material nowadays to understand that , for example, new item models dont take away from fight design, which doesnt take away from cutscenes, which doesnt take away from music, because these things are done by different departments and teams. There is some crossover (for example, any primal with a full set of weapons requires a lot of art assets), but generally there are ways around this.
For example, I believe half of the "levelling" dungeons are wasted. They cause a lot of complaints about queues and blocking the storyline, they are usually done once or twice and then abandoned, and few people are excited. However, the 75 dungeon eats up the same ressources as an endgame 4-man hardmode dungeon! It has sets of visibily distinct gear, fight designs, geography, sound, music, everything! But its throwaway content for the most part, except for somebody unlucky enough to get it in a roulette.
Unless you re-use the dungeon for future content (they did that a lot in classic, see temple of qarn), its very inefficient content that doesnt have a particular fanbase around it.
However, if you take, lets say, the 73 and 77 dungeons out of the MSQ and replace them with a solo duty (using the same geography ) that tells the story, and then use the full dungeon experience and effort for a lvl 80 elite dungeon (same fights just tighter timing, numbers, maybe actually make trash pulls dangerous, but its basically 10% more effort, if even that) you just added TONS of hours to the game.
And dont get me started on reusing levelling dungeons from older expansions as ACTUAL hardmodes.