No, it’s not. Expecting to download content freely from a subscription-based platform, where the creator/producer has ownership, is an unreasonable requirement.
Go buy a DVD, or convince YouTubers to release MP4s for money.
The whole point of those platforms is to reproduce content for my personal consumption. After it is reproduced, no matter how, streamed or downloaded etc, original creator still has the exactly same degree of ownership as before, so their interests are unaffected.
If I don't pay, YT profits from me watching ads so to provide any reproduction capabilities that mean I watch ads less would take bread away from their tables so that's okay. If I do pay, YT profits from that, so I expect it to provide appropriate reproduction capabilities at least by not throttling youtube-dl.
Why would they cater to the needs of captive user base? It's not like there is some alternative and I can stop using YT. I just don't buy YT premium, that's all. In fact I know no one who does, so I guess I'm not alone in this.
That's the perspective of YouTube maybe, but that isn't the perspective of this individual user. That doesn't affect their personal requirements when choosing software. It's a free market.
Go buy a DVD, or convince YouTubers to release MP4s for money.