Builder installed the waste pipe about 4 inches off-center. This made it too close to a half-wall. Instead of moving the pipe, the toilet drain is partially blocked by the flooring. There is no leak but it doesn't flush solids properly. A plumber told us we would have to rip up and replace all our flooring and move the pipe. I'm wondering if an off-set flange will resolve the issue.

An offset flange will not move the pipe. It will just move the toilet. If you just need the toilet to be away from the half wall it may be a solution for you, but if the actual waste line is blocked by flooring you have a lot more work on you hands

"4 inches off-center" off center from what? How much distance to the back and side walls exists. How long ago did he do this job, you may still have recourse with the builder.

A 4" offset flange is a stretch. Could you get by with a 2" offset flange? Let me know. Tom