We all agree with you. The titler does a poor job with partially transparent logos.
The problem seems to be that the people who worked on the titler left the company years ago. Therefore, I don't expect it to ever get fixed.
The new capabilities of being able to edit After Effects text in Premiere Pro indicate to me that the titler is on the way out except for simple things. I have not used it for anything other than a very simple title in many years.
The problem I get is that the title designer is easier to use to get fancy text than After Effects is. Especially because I am used to using Tim Kolb's presets.