Yes, JRPGs have the habit of throwing a lot of text at you, because most of them want to tell a deep story.
The Fire Emblem demo is almost straight ripped out of the full game, so you get a good feel for how long the text passages will be. The two maps you can play are small and only have a few enemies, but that ramps up over time, so the text/gameplay ratio swings in favor of gameplay.
The Etrian Odyssey series has what feels like a lengthy start, but it's actually not a text heavy game. It's just that early on it establishes a setting while the rest of the explanations are kept briefly. Choosing your party can also take quite a bit of time, so it can easily take 30 minutes until you finally set out on your journey after starting the game.
The Bravely Default demo is heavily modified just to give you a general taste of the game. After a short introduction you are free to take on quests and wander around at your leisure.
The common theme is that demos for JRPGs aren't particularly user-friendly. Most JRPGs feature tactical battle systems, so there will inevitably be a lot of explanations. They just aren't something you fire up and play for ten minutes to get a feel for the game.