I am dealing with a problem when exporting the animation I've tried to create on my own. I don't think I messed up something during the animation process, so it has to be something with the output settings. Just like with the donut tutorial (which I exported with the same settings and without any quality loss), I rendered all frames into a separate folder. Only then put them into Video Editing as "Image/Sequencer", chose all output settings, and clicked "Render Animation", as I should. In the Render environment, I see it played in high-quality, just as it should. But then, when I open the video in Windows Player, it seems like it stretches the video to default 1920x1080, whilst it's set to 500 x 500 in the output settings (same whilst animating). I checked all the output settings, but haven't found an issue regardless. I have attached some screenshots to give a clearer view of what I am talking about.
I also sometimes have videos smaller than full HD and when I open them in the player, the video player maximizes its window and makes the video display larger.
However, this is not a problem with Blender, but with the video player. Or maybe with the video format you choose. But if the file says it's 500 x 500 then it is all fine with the file. Maybe there is a setting in the player to play the video in original size.
What I meant by "it is not stretched to 1920 x 1080" is that the aspect ratio didn't change. It might be scaled to fit the height of 1080 and of course this might result in worse quality because not all software scales bitmap perfectly. But again: this is not a Blender problem. By the way, this is how it would look stretched to 1920 x 1080 and your object definitely isn't stretched like that: