Sales reflect reality
First of all I have an iPhone X, because I wanted one.
But I fully understand why most people don't want one.
In terms of flaws, I don't really count the "notch" as one of them. It doesn't affect the way I use the phone. I don't watch videos or movies on a 5" screen.
The first deal-breaking flaw of this phone is its breakability. Dropping glass on the floor usually has one result. I've seen some awesomely expensive cases fully protected by their shatter-prone phones. The cases came through drop tests without a scratch. Unfortunately the same could not be said for their contents. Bottom line, don't drop an iPhone X. You might get away with one or two drops, I even seen it survive drops case-less, but all you're doing is weakening the phone to point where it will shatter.
The second deal-breaking flaw is that it's overpriced by about $300-$400. No phone should cost more than $600-$700. Carriers offering interest-free loans is just code for the re-introduction of contracts.
Finally that battery. A good battery will degrade to about 80% efficiency after two years - if you avoid unnecessary re-charging. Conventional wisdom says that it takes about 500 charge cycles for your average battery to reach 80% efficiency. The problem with the iPhone X and phones like it is they can make use of wireless charging, which is harmful to battery life. Unlike wired charging (modern cables place an almost negligible load on a battery at 100% charge), wireless charges continuously hit the phone's battery with charge cycles, speeding up its end of life.
So to fix problem 1, I won't drop it. Much. To fix problem 2, I got a discount then paid the rest in full. Saving up for a thing you want works. To fix problem 3.. well you can't, but avoiding wireless charging will lengthen the time I need to visit an Apple store to pay for an $80 battery.