That's true, but I want to give you some context here to explain why this decline isn't related to post-Covid.
- Every expansion has grown by a persistent population of around 200,000 or more, especially since Stormblood. Stormblood likely benefitted from a huge amount of marketing, since the game was still not as mainstream as it could be then.
- Shadowbringers catapulted it into the mainstream between its epic trailer, a WoW exodus that began in their "BfA" expansion and continued into further expansions due to the disturbing press. To this day, a lot of current players started in Shadowbringers. The gains, however, were relatively consistent with Stormblood's.
- Covid did not have much impact throughout 2020. There were just the normal patch spikes and that's it.
- In February/March 2021, the game went viral due to the Blizzard scandal and everyone fleeing to FFXIV, which culminated in Asmongold finally deciding to play. So intense was this gain, that we have yet to surpass it. It was easily the game's peak population. And it had nothing to do with Covid whatsoever.
- Endwalker maintained gains, often double what we normally get from an expansion release. Up from the 900k in Shadowbringers, we didn't just settle on 1.1 million, we often reached levels of around 1.4 million, due in part that it was the "end of the arc" and over 50% of former players returned at some point or another to see the end of the story (source: % of past players with Endwalker minion on collection sites). But it was obviously in part due to it going viral and Asmongold. By the end of Endwalker, we were long past Covid and could no longer attribute 1.1+ million to Covid.
- Dawntrail release very nearly reached the peak it did when Asmongold played. It seemed as if the standard expansion gains in Endwalker (of at least 1.1 million) were going to permanently increase to 1.3 million or so, because each expansion usually grows the game that much.
- That didn't happen. The game has shot down to Shadowbringers levels of around 900k.
And we don't need to say why, do we? Despite all the complaints and pessimism, people returned for Dawntrail, then immediately dropped the population
below Endwalker's extremely stable population levels - because people obviously were not happy with the Dawntrail story. And they have struggled with difficulty that is not catered to a wide range of difficulty levels, that SE are trying to solve starting with Pilgrim's Traverse.