Keep in mind, "Raids" are not free to produce. They require new mechanics, new art/design work, story content/cutscenes, and more. They are not a cheap thing, in fact they're probably one of the most expensive parts of the game. They can't just "Produce More Raids" without either a significant increase in resources, a significant increase in time between patches, or possibly removing other aspects of the game. Even that last option doesn't really work, since you can't just move "non-raid" development resources to "raid development". Believe it or not, there is no magic "game resources" that you can move to any part of a project you like. Artists cannot suddenly produce battle content. Battle content designers can't suddenly switch to making cutscenes. Even programmers, which can be more universal, usually need a significant amount of time to adjust to a new team/type of content. If they could produce "more raids and more dungeons and more content" within the same time frame and cost, they would.
On story mode raids, while I understand some distaste for them, keep in mind they have a very large audience right now. Story mode raids exist so that less-skilled or more casually oriented players can enjoy both the story and most of the mechanics. Casual players do not just want to see the cutscenes. They want to experience the fights in a less stressful environment. Story mode raids are brilliant in that they take extremely expensive to produce content that is normally made only for a small portion of the playerbase and open it up to players of all skill levels. The "raiding" community is almost always a very small portion of the community that requires incredibly expensive content to satisfy, so the "story mode" allows more players to use the content. I totally understand the frustration over it, and the desire for more different raids. Just keep in mind that there is far more participation in "Story mode" raids than "Savage Raids", and you'd need a very good reason to change that significantly. If it were possible they could have three difficulties, but they've already stated that it would cost too many resources.
That said, it would make a lot of sense to include more unique phases and mechanics in the savage mode of the raids. I also believe the rewards for it need to be adjusted and changed. They need to at least have unique models for equipment, though I'd like to see them have some special stats or at least a higher ilvel jump. I just think removing Story mode raids entirely would be a huge mistake.