I'm using Premiere Pro 2021 and regardless of export settings, the video has the worst pixelization I've ever seen. Youtube, twitter, h.264 AVI SD or HD, doesn't matter. Audio plays fine but my video looks like some abstract art project instead of a professional high quality video.
Error or problem, Export, Hardware or GPU, Performance
Couple of things to try. Preview Render your sequence before exporting. Does it look OK when playing back (in Premiere Pro) after preview rendering? If it does then check the 'use previews' checkbox in the export window when exporting. This may provide an 'unpixelated' export. Or: Under file menu > Project Settings > Video Rendering and Playback > Renderer change the Renderer in the pull down menu to 'Mercury Playback Engine Software Only' See if this solves your pixelisation problem ... If it ...