There are several problems slowing growth of the industry IMO. When I first looked to buy a dSLR it was because the Sony A100 was the first Image Stabilized, Semi-Pro (feature rich) digital dSLR to go below the magic $1000(USA) price. That was the price experts said the average non-pro would be willing to pay. And the experts were right. Then the Pentax K10D, Oly E510 were even lower with Shake Reduction. The market EXPLODED with sales.
At that time Canon and Nikon could not touch those three. Their kits did not have image stabilized lens yet. The were forced into putting that in lens as a standard feature because the competition had it in their bodies. Nikon did not even give an AF motor on lower models. This allowed the other three to grow. Olympus went a different route some years latter because of company corruption. Anyone remember the rock of a camera called the E3.
Mirrorless compact systems are a big factor in the loss of sales for certain companies. Now the consumer has another choice over the old dSLR type body. Although I prefer and will continue to shoot with dSLR, newbies coming from Smartphones have no problem buying mirrorless systems. They buy both really. This takes away sales. The Smartphone helps IMO generates sales. I got the photography bug from my Kodak Z612. When you get that bug no smartphone, even my Samsung Galaxy S6 with 16mp can touch my K-5. I think many here will know what I am talking about. It becomes a hobby. At the very least I feel people overestimate the Smartphone as a camera killer.
Everyone knows there are too many choices. This does hurt everyone. But the established companies allowed it to happen. dSLR sales were raising because prices were going down. Now no one wants to lower their price. It's like a stalemate with no winners. Price generates sales, or can. The demand is there. The game now should be who can make the lowest cost Full Frame dSLR. Get that price below $1200. But APS size sensors are the sweet spot. Perfect size for body, lens and price. I will continue to preach that.