How to prevent (scurrying) animations from pixelation when uploaded to YouTube?

I’ve created an animation in which a hugh quantitiy of small-scale movements are happening at the same time.
The mp4 file, which results from the render process, displays this animation without any problems … unfortunately, it blurs / pixelates when uploaded to YouTube.

I assumed that this is due to YouTube’s compression. Therefore I tried to change Blender’s output settings so that they meet YouTube’s guidelines (bitrate=10k, GOP = half the frame rate, etc).

Unfortunately, increasing the bitrate (up to 85k) or decreasing the keyframe interval had no impact on the pixelation.

The original output settings:

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Is it possible to optimize the Video in a way, that the pixelation is reduced or prevented?