EOS 5D Mark IV Poor-Quality 4K

[wildwoodphoto]

I am struggling with the quality of video in my 5DiV.

I shot a clip on what I understand is the highest quality possible: in 4k 29.97P MJPG / 1/60sec / f10 / ISO 400 / Camera Standard / 5500k on a Laowa 14mm f4 zero-d. The memory card is a SanDisk Extreme Pro 95MB/s 64GB U3 10C XC1.

The result however does not look 4k. I have uploaded the clip to YouTube here: https://youtu.be/RB-qHm0pa-Y

What are the possible reasons for the quality? 

[wildwoodphoto]

Also here is a WeTransfer link:

https://we.tl/t-nWuMiMDE6B

I can't define what I mean by 'poor' just it that looks like an early YouTube video and not something shot in HD

[wildwoodphoto]

btw, does the SD card make any difference to quality? I'm using a SanDisk Extreme Pro 95MB/s U3 C10 64GB