The steering shaft will do nothing for this it can and should work great being as tight as possible--that's why people buy them. I don't mean to be a jerk, but you need to take a step back and look objectively at what you're trying to accomplish to "soften" the steering and realize that it's clear that there is a fundamental problem somewhere in your steering/suspension/frame. This isn't "a CJ thing" and is not normal AT ALL.
Think about it, your proposing the idea of trying to "fix" this by putting sloppy stock parts back in. Again, trying to point out how this sounds from an outside perspective, not being a jerk.
If you are taking it back to the same shop that can't fix this and just keeps throwing parts at it over and over, you need to stop and think about that.
Have you reached out to a local Jeep club for help? Asking for some folks to come help with an offer of pizza and beer could go a long way here. Someone who has experience with CJs needs to lay eyes and hands on this Jeep. Otherwise find another Jeep shop to try and let us know what their diagnosis is before you pay them for more parts.
If you want to continue blindly replacing parts this way, it's going to be really hard for us to help, and we want to see this fixed and the Jeep be enjoyable.