If you cut the bottom two difficulty levels, you would make raiding content inaccessible for the vast majority of WoW players. It makes more sense to cut Mythic difficulty, it is used by the fewest players. (Not that I am promoting that, just pointing out that it is the most disposable).
Not both the bottom two, one of the bottom 2. Sorry if that wasn't clear enough. Hybridize that level of difficulty so there's 3 total difficulties. (Dungeons are also pretty out of hand now too I think but that's a separate story.)
Or just make LFR an actual tourist mode like it was originally intended that doesn't offer any gear or whatever, but enough people would cry/have cried foul over that situation so...
Gear as the primary motivator for all content is just bad though to be honest, and having it fly out of every system's orifices doesn't help.
The current gear situation is a result of Blizzard caving in to the population that wants something that they don't actually need, which is also a result of pushing raiding and other content on people that has historically had a higher barrier to entry as the only stuff "worth doing" on people that wouldn't have otherwise participated. In doing so they opened up a pandora's jar (it's actually a jar, box is a mistranslation, sorry but it's my snobby historical fact for the day!)
So instead of coming up with alternate meaningful activities for people that couldn't raid or do other high-end endgame stuff, they just watered down what they did have instead for an extremely low lowest common denominator. Mythic raids and rated PvP, etc. are a bone for the top end of players to chew on compared to the other stuff they've experimented with. Admittedly, Mythic raid encounters I'm sure take up a fair portion of dev time too, but that's mitigated by recycling everything else involved from the other difficulties and adding some extras plus tweaking numbers up.
Gear is a crutch now because Blizzard apparently can't think of enough other things, or they want to judiciously ration out any other reward mechanisms they have at their disposal. It's much easier to move a couple numbers around, slapped on the same model with a different tint or minor extra flourish if you're lucky. Gear just happens to be the most visible and obvious reward to give people to increase character power though so…that's what we end up with.
It's probably a cost-cutting measure as much as it is anything else, but enough people have caught on and it's backfiring. At the very least in Legion there was the long term chase of meaningful legendaries (which wasn't great either until they finally put the vendor in, ironically enough.)
Anyway that's my rant and you may disagree, but it is one major factor that I think has led to declining subscriptions ever since the Wrath/Early Cata peak. Market factors/competition sure, but no one can tell me with a straight face that the game is better than it has ever been when the subs are predicted to be around 2 million or less right now from a peak of of 12 million subs and over 100 million created accounts nearly a decade ago. Or the 3.4million in Day 1 sales for Battle for Azeroth. You don't suddenly lose 1.5 million+ customers that are probably quite heavily invested in 5 months or less unless you fucked up big time.
Related, I think classic will be an interesting experiment, but personally I'd rather have an official BC or Wrath server to tool around on. But I know some people are diehard vanilla fans and it will be interesting to check out some things, given that I only really started a real account in early Wrath. Old world and such was still there, but a lot of things were changed already.