It's fixable, lots of solutions, just use the search function and do a bit of reading to see what we've all found to work. It's not a simple solution that's fixed by doing just one thing, I found a combination of things to work best for me.
I understand what you mean, I installed a whole brand new shifter, mechanism, bracket, etc... and still wasn't satisfied until I did all of this. http://www.mustangevolution.com/forum/f358/t324522/
Took it for a road trip yesterday of over 200 miles, had no issues and was a blast to drive.
The only thing that has been proven to fix the MT82 shift quality 100% of the time is a T-56 Magnum XL swap. Other than that, people report that various fixes help them but there is no consistency.
For some it's just a bracket or fluid, some need both, some report they tried both and nothing helped until they replaced the shifter. Others have reported that an upgraded clutch line and fluid flush helped. Some have also reported that stiffer motor and transmission mounts help resolve the issue (I noticed an improvement when I installed my BMR K-member with stiffer motor mounts).
Yes, a T-56 swap is a big deal and costs a significant amount of money, but if you add up all the fixes above (include your time or labor costs) it's not much worse than trying to fix something that's patently broken. You can put band-aids on all day long, but when it's all said and done you will still have the remote shift linkage to deal with, and that will never be as good in a car like this as a transmission with a direct shift setup.