I believe that captions should not be nested inside an adjustment layer.
They should either have a dedicated track like Resolve has or simply be considered as a video track like in Avid MC.
I also think that there should be a global setting (Font, size, positioning) that you can export and share if you have to with other editors. Unfortunately at the moment Premier has the worst captioning than all the other NLEs
We have completely redesigned the captioning workflow in Premiere Pro version 15.0. You will see this feature as well as many other dramatic workflow improvements. Please update to the latest version.
Learn all about the new captions workflow here: https://helpx.adobe.com/premiere-pro/user-guide.html/premiere-pro/using/working-with-captions.ug.html
Adobe Staff - Nate commented
Give the new beta a spin, this has all been redesigned. Details here: