I haven't seen anyone attribute the mainstream success of Final Fantasy to this game. It was definitely VII. VI didn't sell especially well., or grow the fanbase for the series in a tangible way.
Agreed on the game being a bit rough on spots, and character arcs aren't very satisfying. Yet speaking of battles and traversal, it was ahead of the curve. This game isn't grindy, and the battles are quick enough. Random encounter rate is high, but you get a moogle charm for the last third of the game that alleviates the issue.