Yes, I believe it is being worked on. There have been enhancements and bug fixes in most recent versions and updates. At one point, you couldn't even apply a format change to all the captions in a single stream at once. Now you can. And others.
But there are still too many bugs. Some will get sorted in turn; others are difficult because I and other users (and I assume the engineers) have been unable to list the steps that will create them.
Because "captions" are actually many formats with different limitations and workflows, there is also confusion. I don't think captions are worse in PR 2018 or 2019 than previously; they have actually improved considerably one step at a time. But there is still much room for improvement, and there are some bugs that make them unusable at times.
I encourage continuing to report problems and to ask for help, and when doing so, report the specific dot version of PR, the type of caption being worked with (Open Captions, Closed 608, Closed 708 etc), the problem behavior, and whether it can be replicated reliably.
A repeatable problem is captions (open or closed) not burning in when queued to AME from PR. It is 100% repeatable. Fortunately, there is also a 100% reliable workaround. Just set the AME preferences to "Import Sequences Natively."
A not repeatable problem experienced by more than a few users is captions no longer appearing correctly in the program monitor. Sometimes the inconvenience is minor. Other times, it is a major disruption and makes the caption workflow unusable. Either way, extremely frustrating.
Both of these and others are logged as bugs and I believe being worked on. This link takes you to the bug reporting system filtered with the word "caption." Browse through and vote for any that you agree with.
The newest iteration of open captions in PR CC 2019, the caption's start point being dragged instantly defaults the timecode to the start of the previous caption or dragging the end point makes the caption disappear from the caption layer in the timeline.
An older issue, not a problem is working with the captions in the timeline is tedious. Why not add functionality to select multiple captions at once, drag them all to other places, copy and paste captions. I know encouraging diligence is key for accuracy for captions but it shouldn't be an excuse to be lazy with your programming, it shouldn't be a this tedious to work with captions at the end of 2018
Sorry for the frustration. To report quality issues and bugs for certain features (like captioning), please do so where they will be counted, on user voice: Premiere Pro: Hot (3081 ideas) – Adobe video & audio apps
Unfortunately, these forums are for triaging editing problems. Quality issues need to be directed to developers, who are active on user voice, not here. Apologies for that!