Live playback is almost fully flawless. Software like OBS can do transitions and greenscreen / chroma key effects live, without the need of rendering. So it would make sence if "rendering" would at least be as fast as realtime video playback is.
I do understand that videos produced with rendering are not compressed (are they?), but it's very hard to see the compression on the video, especially if video sharing sites like YouTube also compress the video. It would make sence in this case as well to have an option to export the video without rendering.