If you didn't know, light tatsu into sweep is character specific. It won't work on everyone. However, crossup air tatsu into sweep works against the entire cast.
Here's a post from SRK.
You shouldn't be jumping in on anyone unless they're knocked down or if you're out of range from their anti airs. Even if your opponent is knocked down, you still can't jump in on characters with 3f reversals.
Just walk towards your opponent and see what their tendencies are. If they're pressing a lot of buttons you can setup counter hits or frame traps with cr.mp and can link a sweep afterwards. You can also try a sweep if they're whiffing slow moves as well.
You could consider playing a more reactionary playstyle and try to improve on fundamentals. Don't focus on doing combos but rather anti airs, footsies, blocking, ect. Being able to hit combos comes easier if you're more familiar with your character.