First of all, as someone who plays both games these two things (LFR and Alliance Raids) are only similar on the idea they are a large raid that you can queue for that is generally easy to clear. Outside of that they are much different, namely an Alliance Raid is considered as side story activity rather than the actual raid itself just having another difficulty (This is bad and I will explain later) and there’s never been any confusion about who or what it’s for. Alliance Raids have always been essentially alt-gear/catch-up gear for people who don’t do savage and are just capped on tomestone gear, with a weekly clear of the newest raid letting them take a piece to the same item level as Savage gear.
Whereas in WoW, the LFR is not taken seriously nor is it meant to, and a lot of the fights and just the general design encourages a very lazy “hit boss a few times, afk, collect loot” atmosphere. This for a while was not a problem unless important items were in there that necessitated doing LFR because the LFR trinket was better than not having it over other options, most infamously here is Bindings of Immerseus because even the LFR version was still a flat 5% boost to all secondary stats for casters.
Where this becomes a problem from players is that they see that kind of environment, then the constant complaining that “LFR players don’t get any good gear” and inevitably demand more when what they are doing to most people outside of the LFR do not feel is an equivalent level of input for the level of output. It comes off as I guess you could say entitled. Especially when to sate this exact issue for two expansions we had titanforging and everyone remotely serious about their gear hated this system because it just made the treadmill that much bigger because you had to be doing everything because titanforging might make it worth using. This is why melee dps were still running the first actual tier of Legion from 7.1.5 when the raid from 7.3 was in the game, because a titanforged convergence could end up on par ilvl wise with Antorus stuff and its passive made it already a powerful trinket, titanforging prevented its lack of comparative primary stats a non-issue but a grindy one for people.
The other problem that I’m now finally getting around to is its another difficulty when Normal exists and is already basically as easy as LFR. LFR mostly exists at this point because people do not want to apply to groups, here’s more of where that entitlement view comes in play by the way, people think they should just be matched with people, pretty much be unable to be kicked, and be rewarded with good items for it. In a way it caters to players just expecting it all to come to them and fosters that exact view.–
However when I say it’s another difficulty, that means the item levels are based around it. This is why the item level inflation has gotten so bad recently, because LFR of next tier tends to be Heroic of last tier. This is just more item levels they need to jump up. Every tier in Legion was a 45 item level jump effectively, on top of titanforging. In earlier iterations this disparity was not nearly as huge. In Vanilla the stat differences between a tier are not that big in all honesty, most classes are using gear from older raids quite often there as BiS pieces. In Legion we started where M0 was 840 item level or so, we ended where the only LFR player due to titanforging could be sitting on about 960, 30 item levels above what the raid dropped in that difficulty and for what reason exactly? At that point it’s basically forcing huge jumps in item level that bloat the game and inevitably must be turned back, leading to tons of scaling issues all because people deliberately choosing to kneecap themselves at the lowest level of content feel entitled to rewards on par with those from activities/difficulties where one may actually need to apply themselves. When you raise the floor, you also raise the median line and anybody that was slightly above it, or on it has now fallen under it. So people who are running content like m+ for gear from the dungeon now basically have to force themselves into higher level keys to have an acceptable item level, obviously this might agitate them if they are struggling as it is and that being forced on them would be due to raising the item level floor.
IDK why I wrote this much exactly because this post by most people is only going to get seen of as “This guy things LFR players shouldn’t have the best gear in the game” and little else. Another reason why people are also negative towards LFR, a lot of forum discussion around it basically boils down to kicking and screaming and refusal to actually acknowledge any negatives or raise any valid points.