This isn't about sales Mr B. this is about impacting future FFs and while VII is a success as well the issue here is that everything you just attributed to VII can be traced back to VI and other 16-bit titles. The fact VI pioneered more interactive design that later games like Live A Live, CT, and the PS1 era FFs continued to build upon shows that evolutionary speaking VII owes some of it's successful design to VI. VI utilizing universal sprites for combat and story scenes (something VII doesn't even do) already showed that Square were moving towards making seamless transitions and frankly Secret of Mana and CT both beat VII to the punch on a technical level though VII's contribution is certainly the more impressive version but CT already had beaten VII to the seamless game-story-minigame transition before VII pulled it off. So yeah... VII owes VI.
You forget that I said the Esper/Relic system with Relic's providing changes in characters skills as long as the item was equipped combined with having your magic leveled up by equipping various espers that taught different skills as you gained AP. On paper the system have some similarities in execution, it's just that VII basically combined both concepts with materia being items that must be equipped to gain their ability but multiple abilities can be learned by leveling them up with AP. They are not the same system but I feel one can see a link in how they both grew from FFV's Job System (which is frankly vastly superior to both). VI's system was simply trying to reinvent the wheel and Square/Squenix has being pursuing that ever since.
I do feel the story is revolutionary for its time but so were many of its gameplay elements, I mean incorporating slot machine mechanics, SF move sets, and enhancing story sections with game mechanics were not very common in the early 90s and Square pursued the trend well into the PS2 era. I guess it would depend on what you felt the story did that was truly novel as all I can think of is the ensemble cast which is rare for the genre, even today.