Why is my footage degraded?

I edit with an MSI P75 Creator in resolve 16. I choose the 2160 timeline settings and the preferred YouTube 2160 export settings using NVIDIA. I shot this in Q0 at 60 FPS on a T5 and slowed down 50%, am I possibly slowing down too much? My main complaint is the waves at the end of the video rendered to be very blurry but raw they looked amazing.

First of all, waves are very difficult to compress, you need high bitrates. And then, optical flow has a hard time with waves too.

Try two steps: first export in a higher-qaulity, like Cineform or DNxHR. If that looks better, it's the compression and you should compress externally with Handbrake or upload your rendered files directly to YT.
If that file rendered in a better format looks wrong too, experiment with the settings, maybe speed warp can help (slow). And next time do slo-mo in the camera, if possible. Speeding up is not a problem.

First of all, waves are very difficult to compress, you need high bitrates. And then, optical flow has a hard time with waves too.

Try two steps: first export in a higher-qaulity, like Cineform or DNxHR. If that looks better, it's the compression and you should compress externally with Handbrake or upload your rendered files directly to YT.
If that file rendered in a better format looks wrong too, experiment with the settings, maybe speed warp can help (slow). And next time do slo-mo in the camera, if possible. Speeding up is not a problem.

Thanks for your reply, would it be better to shoot 3:1 rather than Q0?

I recommend outputting with an uncompressed format like dnxhqr 10 bit. Then compress it yourself with handbrake h.265 with a high bitrate. It takes many hours longer but you will get infinitely better results that way.
Here's a sample of what mine looks like when I use the above method.

Or, if it's not too big, send the DNxHR file to YT, they recompress anyway.

Yes. that is true too. It would have to be a very short video for it to be sent without the handbrake step though. Youtube has a maximum file size of 128 gigs.

Yes. that is true too. It would have to be a very short video for it to be sent without the handbrake step though. Youtube has a maximum file size of 128 gigs.

One suggestion: don't use YouTube. There are higher-quality platforms available that will give you a lot more bandwidth, like Vimeo Pro and Frame.io. But there's a price to pay for that kind of bandwidth.