I used to have that problem in 1080p vids, and it did seem to get worse recently, and I think I found out why. Just so you know, it doesn't really do any good to use more than 12,000 bitrate on 1080p YouTube uploads, because their conversion software, which converts it to a streamable format, won't make use of any more than that.
It's said if your channel is very popular, YT will use much higher bitrate. Not sure if it's true, but it would make sense since very popular channels are worth more in ad space . At just under 2000 subs, and given the problems you're having, you likely don't qualify. I know I sure as hell don't.
It used to be you could circumvent the low bitrate conversion of 1080p uploads by slightly resizing them to 2048x1152, but the geeks that run YT caught on to that trick and now they only apply the higher conversion rate to actual 1440p uploads.
I was resistant to trying a 1440p resize, thinking the lack of pixels would surely blur the vid more than sharpen it. Since learning YT applies literally 3-4 times the bitrate for 1440p though, I decided to give it a try. It seems ever since 1440p became hugely popular, YT has given 1080p a disproportionately low amount of conversion bitrate.
The tool I use for editing, resizing, and compressing, is very basic. It's called Avidemux. One of the best things about it, other than being fast at encoding due to it's basic, streamlined design, is it has a very high quality two pass ABR (Average Bitrate) compression option.
YT states to use 30,000 bitrate for 1440p uploads, but I have found it depends on how graphically detailed the game is. For instance with The Evil Within, 20,000 worked fine, but Ghost Recon Wildland's dense foliage and faster paced action, required 30,000.
Here is an example of the same mission in GRW, one a 1080p upload at 12,000 bitrate, the other resized to 1440p at 30,000. When you compare the escape footage after stealing the car, especially while zoomed fullscreen, the differences are very easy to see. Note you must always select the highest YT viewer res, not leave it at the "Auto" version of that res, to ensure max stream quality.
1080p Upload @ 12,000 bitrate
1440p Resized Upload @ 30,000 bitrate
The Evil Within Resized to 1440p at 20,000 bitrate
Notice how in TEW, even the fog isn't pixelated, and at just 20,000 bitrate. Like I said, the bitrate you need depends entirely on the overall graphics detail of the game's textures.