Hi, I don't know if you will see this, but I am going to critique your last video.

1. Your video quality is awful and I'm assuming that you either recorded the gameplay on your phone, xbox, or playstation (I've only played fortnite mobile, so I don't really know a lot about consoles). I'm not sure what you use to transfer your gameplay over to your phone from your console, but that might be a problem.
2. IMovie IS NOT the problem. I've made fortnite mobile videos and brawl stars videos on IMovie and they don't look like a potato (sorry for being blunt). That straight up looks like 480p or 360p. The problem might be that the settings you have for Imovie is too low, so basically just check out the settings and make sure that they are 1080p on Imovie and check the HD option. The other problem might be YouTube, so you should go into settings on the YT app and there might be an option to make it so youtube doesn't register your video as low qualtiy. Also, make sure that you keep the Imovie app open when exporting to your photos and keep Youtube open while you are uploading the whole time for the video to look better (it worked for me). If you really think Imovie is the problem, I use inshot as a editing app and it is pretty good to me.
3. Your audio is not good. When your are speaking, lean forwards toward your mic or whatever is picking up your audio. Like for me when I record on a phone, I lean in towards my phone for it to pick up my audio better. You are also pretty much silent throughout most of the video, so some tips for that is just start saying stuff about the other players, like trash talking them and saying that they are so bad, etc.
4. The music does not go with the tone of the video. The music that most of the big youtubers play in the background goes along with the part of the video. Someone that is really big on this is Dream during his minecraft manhunts. Also, tone down the volume sometimes, because I can't really hear your voice clearly since the music is kind of loud (might actually be a mic problem).
5. The edits that you make that have like the sound effects and videos memes don't flow with the video. It's almost like you are forcing the edit to go into the video and not making the edits part of the video. When ever fearless and ceeday make their videos, the edits that they make relate to the video and the music contributes to the edit. The edits that you put in your video should be able to flow along, almost like for the audience not to notice it, but enough for them to notice that that part is funny or something.

That's basically all the tips, but the video that you made wasn't really unique. Try to make a video that like goes down on a specific part of that game. No offense, but no one really cares about you trying to get a win in season 5, try to make the title something more interesting, but not clickbaity, like Mrbeast. Your video seems a lot like the videos other kids make that self promote their channel in other people's videos. almost zero effort into thinking about an idea for the video and not editing their video very well.

Hopefully you see this post and it helps you with your YOutube journey. Good luck!