I like missions, but there are basically two kinds...iron missions, and others. The irons are pure grind missions. They were the first missions added to the game, to make grinding less boring, and I think they do that. Same with the daily missions, and if you are going to hunt anyway, pick up the iron mission if it is available. It is pure added eco if nothing else.
The other missions are more varied...there are short one-offs and epic mission chains. Some are grinds, some are fetch, some are explore, and some are just fun. Some have rewards and some don't. I enjoy these, and every VU I check to see if we've gotten new ones. Unlike the irons, many of these missions are geared toward newbies--part of MA's efforts to attract and retain new players, a trend that's likely to continue. Not a challenge for older players, but they can still be fun.
So I enjoy doing missions, but there are only so many, and then EU goes back to being a sandbox with iron missions, which is also okay.
BTW, if you haven't done it yet, I suggest doing Hunt the Thing next tine you're on RT. It is for lower levels, but still widely considered one of if not the best mission chains in the game.
EDIT: Oh, and you can track up to five missions. You can click one to make it active, meaning it shows waypoints.