Using a push block instead of a coping sled eliminates the need to be at 90* also. If you watch Marc Sommerfeld's videos on you tube that's how he does it. Many of us don't bother with a t track for mitering but some still like to have it for using feather boards but you still don't need to be perfectly 90* using a feather board either. A router bit is not like a table saw. It doesn't matter what direction you approach it from it's still the same.
Someone I consider a master woodworker once told me that a master woodworker is not someone who never makes mistakes. He is someone who is able to cover them up so that no one can tell.