You should know better.
"coupled with competition from the likes of Apple's iPhone and Samsung"
Those 2 have been bleeding share for years too, Apple has a better year now on a huge upgrade cycle since their installed base was on tiny toy screens but share loses will resume if they don't do more. Samsung is just offering less and less for more, giving up share for margins.
"Although known for lower-end handsets, the company has tried to branch out into the higher-end market -- one that is dominated by the iPhone."
On what planet is HTC known for lower end handsets? They had lots of high end devices well before there was an iphone. Then , calling the iphone high end is debatable. research firms categorize handsets by retail price but that's the wrong way of doing it for everybody except the handset makers. Users do it by specs, component makers would be better served if it was by BOM/specs. The iPhone 6 BOM must be some 150$ now, someone like Xiaomi or Meizu would sell such a device at 200$. Defining the categories by price is really bad research. If you take the Xiaomi Redmi Note 2 at 125$ in China vs the Galaxy A7 at 4 times more in China, the devices are similar, the Xiaomi is faster, the Samsung is shinier but labeling the Xiaomi as low end and the Samsung as high end is just ridiculous. Sure too many consumers are irrational and uninformed but considering all consumers to be that and categorizing devices by retail price when there are such huge gaps is bound to paint the wrong picture about the market. To make it worse research firms also ignore carrier subs, why count a device as 700$ when it's in practice sold at 200$ or less.
HTC dies on many mistakes over the last few years and the fear to adapt to new realities. Old phone makers need a 50% price cut, how they get there is up to them - this includes Samsung, LG, Sony and all the others non-Chinese players.
Lenovo is in trouble on carrier subs declines in China last year. They are yet to shift from carrier phones to full retail in that market. Currency in some other markets made it worse.Competition in India from Chinese players also hurt Moto, although Lenovo overall is doing ok in India. The good part is that Lenovo's CEO is a smart guy, just not sure he picks the right people for the job.
Going forward the competition has room to become a lot more intense if old school players decide to adapt and compete, if carrier subs shift a bit and if midrange SoCs go from many small cores to a a couple big ones and some small ones- this last bit is more important than it seems, it would allow for sub 200$ devices to offer a great experience.
Hmm ,you know, the US is in a bubble, the smartphone market has been killed by carrier subs ,very few models for sale, poor prices and the press is not used to look outside since in PC the US was the key market. You should buy something like the Xiaomi Redmi Note 2 (no US LTE bands but price per specs likely the best phone in the world right now - won't last more than a few months) or at least a Moto G ( not ideal since those specs are half the price in China/India) and use the device for a few months even if you hate it at first. It's hard to imagine the ocean if all you've seen is the desert.