There are two things holding IC's back.
Stages.
People playing gayer on stages.
Once people figure out that even the "neutral" stages like Battlefield, Smashville, Lylat, Ps1, etc aren't "lol **** on Neutral Status" for IC's, then it's obvious they are not that good. First match of the set, ban FD/strike it, and strike something kinda dumb like Yoshi's Island (playable, but most characters can try for a better matchup on Smashville or Battlefield or whatever). Almost any stage at that point is pretty good against IC's.
Smashville: Camp the platform, glide under the stage, edgecamp while platform is near and then go back to platform camping, attack them on stage while retreating to platform, etc.
Battlefield: Camp the platforms, glide under the stage (kinda small stage, but it can work), go safely from platform to platform keeping horizontal spacing from them.
PS1: Camp the platforms/areas they cannot approach you safely in. Some characters can go offstage pretty far and then come back safely because of the stage transformation (burning tree, windmill, etc).
Lylat: Oh dear lord. This stage is like heaven against IC's. If you get grabbed here, chances are you did not play gay enough. Very large tilting stage with platforms galore, lots of vertical camping space, very good stage for most characters to take IC players to.
I have so many people tell me "But DMG, you can't camp the platforms against IC's, their Uair is too good!" and then you see people Dair camping them all the time with MK, you see G&W players playing keepaway, Lucario, Wario, even Snake and Jigglypuff. Like once you learn to pick a good character against them and camp them appropriately, then it starts to become clearer that they don't do so hot, at least not top 5 level. Even if you consider the character currently underrepresented and in the future they will have more people behind them, that's not a big enough/valid enough reason to put them at top 5.
With that being said, they are still obviously a good character. I would be a little surprised if they were not top 10, however at the same time I do see a lot of other characters being more solid than them. Really IC's to me seem like a sharp Chess Defense for Black, say the Sicilian Dragon. White probably has the advantage, but the game becomes very dynamic and full of tactics for both sides. IC's are a very dynamic character that certainly can have the advantage against pretty much anyone if they make a slight misstep, but if the other person plays up to par the IC's will find themselves winning less/clearly at a disadvantage.
Stages.
People playing gayer on stages.
Once people figure out that even the "neutral" stages like Battlefield, Smashville, Lylat, Ps1, etc aren't "lol **** on Neutral Status" for IC's, then it's obvious they are not that good. First match of the set, ban FD/strike it, and strike something kinda dumb like Yoshi's Island (playable, but most characters can try for a better matchup on Smashville or Battlefield or whatever). Almost any stage at that point is pretty good against IC's.
Smashville: Camp the platform, glide under the stage, edgecamp while platform is near and then go back to platform camping, attack them on stage while retreating to platform, etc.
Battlefield: Camp the platforms, glide under the stage (kinda small stage, but it can work), go safely from platform to platform keeping horizontal spacing from them.
PS1: Camp the platforms/areas they cannot approach you safely in. Some characters can go offstage pretty far and then come back safely because of the stage transformation (burning tree, windmill, etc).
Lylat: Oh dear lord. This stage is like heaven against IC's. If you get grabbed here, chances are you did not play gay enough. Very large tilting stage with platforms galore, lots of vertical camping space, very good stage for most characters to take IC players to.
I have so many people tell me "But DMG, you can't camp the platforms against IC's, their Uair is too good!" and then you see people Dair camping them all the time with MK, you see G&W players playing keepaway, Lucario, Wario, even Snake and Jigglypuff. Like once you learn to pick a good character against them and camp them appropriately, then it starts to become clearer that they don't do so hot, at least not top 5 level. Even if you consider the character currently underrepresented and in the future they will have more people behind them, that's not a big enough/valid enough reason to put them at top 5.
With that being said, they are still obviously a good character. I would be a little surprised if they were not top 10, however at the same time I do see a lot of other characters being more solid than them. Really IC's to me seem like a sharp Chess Defense for Black, say the Sicilian Dragon. White probably has the advantage, but the game becomes very dynamic and full of tactics for both sides. IC's are a very dynamic character that certainly can have the advantage against pretty much anyone if they make a slight misstep, but if the other person plays up to par the IC's will find themselves winning less/clearly at a disadvantage.