I did play Saga Frontier when I was younger, but only a friend's copy. I never really had the chance to sit down and play through it, but I do remember liking certain aspects of it. Finally having a chance to play it again, I cleared two character stories and find myself having no desire to pick it back up. I suspect this review isn't likely to win me many fans.
Saga Frontier doesn't feature one main story, but instead, each character has their own story you play through. I will be spoiling one of them just to explain to you what to expect, at least the two I played through. You play as Lute and you leave home for adventure. A guy named Mondo let you ride with him, then you randomly come across a captain who is an anti-trinity activist who is trying to stop Mondo from forming a small army, and also your father was an anti-trinity activist. Oh and sudden twist you were a Trinity Agent the whole time. That's the entire plot when you play as Lute. Riki is not really any less stupid either. There is virtually no time developing any of the characters, and the story beats just kind of happen. The whole scene you meet the captain lasts maybe a minute. Maybe other character stories are more interesting, but the plot is such a rush job here.
Even the world just feels slapped together. I don't understand where any area is in relation to another. You travel by some kind of spaceship between different areas. One area has a bio-lab full of scientists gone crazy, there is a snowy area that seems inhabited only by Virgil, and near-omnipotent being compared to the rest of the world and a few other places that just don't feel like they exist as part of the same world. I really cannot find a place to praise the games writing because of how slapped-together the whole narrative feels.
Gameplay ends up being a mixed bag. I like the way you get stronger. Rather than levels, stats raise based on how fights go. Use more magic, your magic abilities get stronger. The same applies to hitting, getting hit, etc. Learning new abilities requires you to use appropriate weapons, so the more you use a sword the more sword techniques you learn. It's a similar system to what was used in the original Final Fantasy II on the NES, but a much easier-to-use and understand system. Where things get frustrating is the Combo system. Certain abilities have a chance of linking together and getting stronger, but the game never explains how this works. They expect you to just figure it out. The problem with that? Well here is an old Gamefaqs thread describing how this system works.
https://gamefaqs.gamespot.com/boards/198537-saga-frontier/51196794
This is so much stuff to learn and understand just to make use of a system. And if you want to beat Riki's story, one of his last fights requires you to either understand how this system works or get lucky enough to have seen multiple combos and remember them. I won't even get into the system for power up Monster Characters like Riki, another thing the game does nothing to explain and requires large outside resources to be able to make use of.
There are a lot of other neat things about the game. Limited item space makes you have to plan your gear carefully, LP limiting how many times a character can go unconscious/get beaten while down on the grown before you have to return to an inn to use them, and other similar systems make the battles interesting. Despite how poorly the game explains them, I like that there are different systems for strengthening different races. Humans, Mystics, Robots, and monsters each have different ways they function.
In the end, I don't think Saga Frontier is a very good game. Too much is badly explained in the game, and the narratives feel really rushed and slapped together. That said, there are a lot of good ideas and a very unique and well-crafted leveling system that hasn't been replicated since. I can see why people can look past a lot of the game's flaws.