Go to training mode, turn on input display and tell us what you’re getting.
You should know, some of the characters you are listing use more than a simple tk motion. Cammy for instance can only use a back tk motion on ex’s, the normals must end at up forward. The only real trick with Sim is waiting for him to get off the ground before hitting the buttons. With Viper, I think I remember something about command overlap with tk motions and super jump, but you’d have to ask someone more familiar with viper than me.
I have like no experience with Makoto and Adon, so I don’t know what to tell you there.
But yeah, it’s probably an execution problem.