The FFXIV team is really good about not pressuring people to play. The producer specifically says it's a goal for people to drop their subscription whenever they want and come back when they're ready.
Most grindy things are optional, as things like gear progression are set up to take up time if you're up to date on the new content, but be easier if you're catching up. (And that whole tomestone system is being redesigned in the next expansion, to take away pressure to play every day.)
The free trial is very generous, and the full game is usually sold so you buy all-but-the-latest-expansion for one bundled price, which often goes on sale.