Ok, Chrono Trigger is one of my favorite games of all time so I'm going to try to make this as objective as possible.
Flaws first.
1) The characters are notoriously cardboard. They have very little depth. The upside of this is that it seems intentional. They're all archetypes and because they're so different from each other they play well as an ensemble. But there isn't much "growth" so to speak. It's actually kind of Dragonball-esque in that way. And so while some people consider it a flaw, I think this actually leads well into the strengths, which I'll get to in a sec.
2) This could be a flaw or a strength depending on your angle but it's very easy and relatively short.
Now the strengths.
1) It doesn't require much of a time investment. This is why the above flaws actually can help depending on how you want to play. With a lot of RPGs you have to put in at least an hour or two to feel like you made any progress. In CT you can play it for 20 minutes and actually feel like it wasn't wasted just fighting random monsters in the same cave. In that sense, it's very rewarding with little effort.
2) This could go one way or the other but I find the game very charming. The characters, plot, villains, it's all just "fun" if you catch my drift. No complex psychological examinations of the cast. No moral ambiguities to explore. It's just fun.
3) There are no fetch quests and annoying backtracking. This is probably its greatest strength considering most RPGs of this era were notorious for doing things to you like "I would take you across the ocean to the next continent but monsters stole my sail. Go into the random cave to the south and get it back." Everything you do is relevant to the plot. That lack of filler is actually the reason it's so short.
4) I would say it has the highest replay value of any RPG. This is due to both the New Game + feature (something more games should take advantage of) and the fact that the game isn't tedious in the least. Even if you've seen all the endings it's the kind of game you can play just for the hell of it much like you would a Mario game. In that sense, it's an RPG with the replay value of a platformer.