If you mean a low resolution, you can use any of several browser extensions (I like Iridium) to automatically "manually" select the resolution right when the pa

If you mean a low resolution, you can use any of several browser extensions (I like Iridium) to automatically "manually" select the resolution right when the page loads for every video, and this will also increase your maximum buffer from 20 seconds (?) to 2 minutes, which is nice if you're on wifi. If you mean on high resolutions the videos still look terrible, that's because the av1 versions of many videos look very bad above 720p on purpose if they're mostly watched in certain countries (can't find the source now, so treat as hearsay) where most viewers are on smartphones. You can mitigate this by going to settings > playback and performance and select "Prefer AV1 for SD."