I'm using Kdenlive for my Youtube videos. I've tried the Youtube option in render options or H.264, but in botch cases Youtube says that the video is in bad quality.
What resolution is your source video?
What bit rate are you encoding at ?
Is YouTube reporting a warning/ error or are you just unhappy with the quality of the result on YouTube?
Does the result look ok before posting to YouTube?
Run ffprobe on your source and result videos to get info on stuff about them and post the results