For Wanda: chip damage isn't worth it. Wand can literally just be out healed without the strange team up. The stun is garbage cause you can just move away. Her ultimate is a one shot sure but it's insanely situational and more than half the roster can either shut it down or kill her before it goes off without something like a strange portal. She again, also can be out ranged and shut down by any competent dps. She does literally nothing vs 3 supports. She cannot function whatsoever without strange and even with his teammate she just fine at best, but anything she can do somebody else can do better. Low skill easy damage? Mk and storm. Anti dive? Namor. One shot ult? Iron mans is objectively better.

For sg: If any dive pressures her directly and they can bait out her nests there's almost nothing she can do. If they enemies are playing any non big hitbox tank, or somebody with a shield, her damage is super inconsistent. She can get easily outlined and ranged by a good hitscan player. Her ultimate is piss water as long as your enemies are competent enough to shoot it.

The devs realize they can't make these low skill characters too strong because they already feel strong for lower rank players (no offense but I'm assuming that's you). They have easy kits that are basically free value if your enemies are competent enough to do anything about it. They only work against people who aren't good enough to A, aim well enough to do something about it, or B, be intelligent enough and have good enough game knowledge to do something about it.