Contrary to popular belief, WoW's convenience and "casual" features are not designed to appeal to casuals. Rather, they are designed to appeal to WoW's current core target audience which I will NOT explicitly name until the end of this post because without context, explicitly naming that target audience would result in a ban.
-AP and similar endless progression grinds-
There is nothing casual about having to follow a set routine every day in order to progress your character. World and daily quests encourage you to log in every day and do the same repetitive tasks in order to increase your character's power. World quests are by far the bigger offender because their introduction concurred with the introduction of Artifact Power in Legion. With old daily quests, you could get away with doing them for several weeks per character because you got your big power reward upon achieving revered / exalted and further repetition provided no material benefits other than gold. Despite being named "daily" quests, you didn't actually have to do them daily. You could do Sons of Hodir every other day and you'd still unlock your shoulder enchant in the end.
World quests, on the other hand, encourage repetition over the course of the entire expansion. There is no big power reward upon achieving revered / exalted. Rather, minor power rewards are spread over the entire set of world quests that you could potentially do over the course of the expansion. By skipping a day of world quests, you are not postponing your power reward. You are actually missing out on your daily power reward that will disappear at the end of the day forever. As a result, many people feel like they're "falling behind" if they don't actively do world quests. This never happened with old daily quests.
Who does this feature appeal to? WoW addicts who feel like they need to get their daily fix of WoW. What does this feature induce? Compulsive addiction towards logging in daily to get your "fix" aka minor power rewards from world quests.
-Titan/Corruptforging-
There is nothing casual about having to repeat the same content in order to get the best reward. In older iterations of WoW, you'd move on to the next level of difficulty after exhausting all available rewards from your current level of difficulty in order to grow your character more powerful. Once again, moving on to the next level of difficulty did not necessarily mean that you were going to do content that was harder from a mechanical point of view. It meant that you would do content that was more difficulty from the point of view of your character's stats. Outside of the crazy stunts that world top-100 guilds pull during WF races, there's nothing inherently difficult about WoW's raids. It's just a learning experience that's pretty easy to execute once you've pulled the boss a dozen times or so.
The big thing about the old system of character progression is that it was finite. Once you exhausted a particular level of difficulty e.g. dungeons, you'd move on to the next thing e.g. raids and wouldn't spend nearly as much time doing dungeons. You'd maybe do them once a day or so for badges (and that was only until you bought all the gear that was purchasable with badges).
Titan/Corruptforging broke the exhaustability of content. With these systems in place, the person who farms the MOST content is the best geared rather than the person who follows the progression path from easy to more difficult content.
Who does this feature appeal to? WoW addicts who feel like they need to get their daily fix of WoW. What does this feature induce? Compulsive addiction towards repeating the same content ad nauseum to get your minor power increase from titan/corruptforged gear.
-LFG and LFR-
There is nothing casual about obliterating WoW's social experience in order to make running group content more convenient. In reality, many people who play WoW exclusively for social interactions (people who roleplay in major hubs and don't bother progressing their characters otherwise) would argue that it is THEY who are the most casual of WoW's subscribers.
Adding LFG and LFR along with the introduction of world quests and titan/corruptforging led to the perfect shitstorm in which you would be invited to groups not on the basis of your sociability, but based solely on your stats / rankings / ilvl. In older iterations of WoW, you did not have access to an infinite supply of players willing to run a particular dungeon / raid with you and you had a harder time vetting them because tools like raider.io had not been made yet. Rather, you'd invite people based on their willingness to do a particular dungeon / raid AND their gear and social standing on the server. Now all the people in LFG might as well be faceless drones with IO scores branded on them. There's no need for social interactions. Addons, raider.io and LFG do all the talking for you.
Who do these features appeal to? Socially awkward people who weren't able to join guilds / be friendly with people / build a reputation in previous iterations of WoW. By introducing these features, Blizzard encourages people to compulsively grind power increases through world quests and titan/corrupforging in order to improve their raider.IO scores / ilvl / whichever flavor of the day metric is considered the most important.
It's not hard to see why Blizzard went in this direction. In order to retain people who are not addicted and are socially well-adjusted Blizzard would have to release quality, FUN content. Why would those people stay if the content Blizzard releases is shit and their friend networks quit? That's right, they wouldn't.
Addicted, socially awkward and otherwise mentally unwell people, on the other hand, don't really care about the quality of content. Rather, it's the quantity they're after. They want their daily fix of WoW no matter how bad it is and Blizzard is more than happy to design infinitely grindable features to satisfy their cravings. The longer the content takes to do the better. Why bother designing fun content when you can pump out crap after crap after crap? After all, quantity is much easier to do than quality.
The shift already started to occur during the Cataclysm when people cried about there being "nothing" to do at max level while never stepping into raids or the arena. There is absolutely nothing casual about modern WoW's infinite grinding. A casual can easily clear all current raiding content while investing minimum time. I played no more than 12 hours a week back during Vanilla-Cataclysm eras and still managed to most of then-current raiding content. That is what I would consider a casual. I can't call myself a casual anymore. I have to dedicate at least two hours a day and that's WITHOUT raiding to just staying relevant with all the endless grinds. With all this bonus shit that I have to do on top of holding down a job, looking after myself and maintaining my hobbies and irl relationships, I don't see myself being able to keep up with these grinds much longer. But Blizzard doesn't care because their addicts will keep giving them endless $$$ as long as they keep pumping out infinite, boring, repeatable, grindy content.