Okay let me try this. How do you realistically and effectively train offline when no one is offline play with you?
Play online a lot and force yourself not to use certain things you know don't work offline. For example, don't mix up with Bass 1P after a pickup. It's a stupid mixup that gives you nothing and it is incredibly reactable if you're waiting for it.
Is it effective online? Sure. But offline it will probably just get you raped when you run into a tougher opponent.
Understanding things like that can allow you to get "decent" practice online so long as you force yourself to play honest. If you don't yet have a feel for which moves are more easily abused online, then it can sometimes take a trip to a tournament and watching part of your routine get blocked over and over before you finally realize what it is you have to cut from the program.
The only frustrating part is that you'll have to fight people who aren't playing anywhere near as honestly because they have no desire to pursue an offline career. So they will always have an advantage on you in some regards.