Let's say you've been farming ICC for WOW Classic TBC Gold a few months in order until you become Invincible. It's like getting a level 4 for effort (because time spent) for an 8-level reward. Although there's less effort to obtain a reward it is still more difficult to get a less valuable reward. To find the top mount, you don't have to click as many times as you're able in the store. However, it's possible to run the same raid over several months to get an attractive mount. Blizzard has made it so that mounts are no any longer a subject of discussion. It's possible to say that store mounts are 0 effort as you're simply getting it in the game for free (6-month sub). It's awesome to be able to have access to the top content in the game with no effort. It makes you feel like you've cheated or won in a significant manner. It's not nice to have to then be extra determined to receive less of a reward. This is why mythic raids are so difficult to conquer. This is also the reason why nobody spends days in clearing mythic. It is possible to replace mythic with the heroic version within the next tier, which requires only two weeks when compared to months.
This happened with Naxxramas. Naxxramas is the company that caused this. This was the problem with gear. Then they solved it by using mounts. Blizzard has a knack of making you feel like you're just wasting your time. Sub numbers are then dropped before they can fix the anti-QoL system after the game is dead.
In reality, 9.1.5 is only 9.0, but it's fixed. This means that the new content will not be available to players until 9.2 however it should be 9.1. That's the reason that not many players are resubscribing for 9.1.5 as the new content won't be available until 9.2 in which case you'll be able to buy WOW TBC Classic Gold play the new content on fixed systems.