Caustic and Wraith's abilities seem to exist on the opposite side of one another so far as Apex Legends is concerned, but both need to be fixed for different reasons. Caustic's Nox Gas Traps can be infuriating by anyone not playing Caustic, and Wraith's tactical doesn't really add much to her overall skillset at all.
Wraith and Pathfinder both were still the most popular picks in Apex Legends Season Five, but that's likely due to Wraith's hitbox being the smallest, and Pathfinder's being famously broken, not their abilities. Regardless of why Wraith is being played, her tactical ability is still boring, and a better version of her ultimate can be found while playing Revenant.
Caustic, on the other hand, can get kills just by standing still in his own Nox Gas and firing on any blind enemy that happens by. Basically, Wraith is boring to play, Caustic's tactical is overpowered, and both Apex Legends characters need changes.
Apex Legends: Wraith's Abilities Need Changes
In Apex Legends, Wraith's Into the Void is a shorter, worse version of Octane's Stim tactical. Sure, Wraith becomes invulnerable for four seconds, but she also does no damage, can be spotted pretty easily because of the bright-blue trails she leaves behind, can't open doors, and doesn't even gain any vertical mobility like Pathfinder does. Granted, she was one of the characters originally introduced with Apex Legends, so it makes sense that her abilities would be superseded by newer characters, but it also means there's been nearly two years to fix them.
For some solution ideas, Into the Void should - at the very least - be harder to track. It doesn't much matter if Wraith can't be damaged for four seconds if an enemy player can just track her for that time period and then kill her while she's coming out of the animation. Her ultimate (Dimensional Rift) has the same problem, but it seems more fair because it allows for Wraith's entire to team to portal. Into the Void should function like Wraith is actually going into another dimension. Not able to open doors? Fine, let her walk through them. This would play into the character's aesthetic, wouldn't be hard to implement, and makes her ability feel more original. For something more major, going through walls could be an option, but that seems like a bit too much.
Apex Legends: Caustic's Abilities Need Changes
Caustic's Nox Gas is unpleasant for everyone involved. His teammates can't see enemies, and his enemies are slowed, and they take stacking damage that ignores shields. The size of the traps actually seems fair, as well as Caustic's hitbox being larger, especially when a Caustic is in their own Nox Gas. His ultimate (Nox Grenade) takes quite some time to use, which helps compensate for it basically destroying someone on a hit, but should probably have a smaller radius.
For minor solutions, Nox Gas' damage shouldn't stack (or, at least, it should stack less). Decay abilities are kind of Caustic's thing, and also keeps his tactical from just being the same as Bangalore's. The tick-damage could use a bit of a nerf because of the blindness aspect, however. For more major changes, Caustic could be allowed different types of poisons, and given the ability to choose from them for his tactical. He could choose to blind an enemy entirely (like a flash grenade that hits the HP a little), slow enemies in a radius, and maybe one that decays health like his gas does currently. For Nox Grenade, changing his ultimate to one that temporarily de-evolves enemy shields would be pretty cool.
Wraith and Caustic aren't the only characters that need changes (looking at you, Crypto) but these fixes would surely make the characters more interesting. Whatever Apex Legends does next, adding cross-play is certainly a great start to improving the game.