Are 1080 and 720 videos supposed to look significantly worse on a 4K TV?

Just recently got my PS4 Pro and Samsung 49KS8000. The Pro supported games I've played and 4K videos I've streamed have looked great. But all the non 4K videos on YouTube look considerably worse on this tv, like they look super pixelated and it's such a bummer because i watch a lot of YouTube on my tv. I'm hoping I'm just dumb and don't have some settings right or something but here's what I can tell you about my setup so maybe someone can help.

I have the tv calibrated according to the rtings.com KS8000 calibration guide, which I have seen recommended on here. I have the settings calibrated under Game mode and Movie mode. YouTube videos still look like shit no matter what mode I have the tv in, even the standard and natural modes, which I haven't even adjusted any settings for.

I have all the video output settings on my PS4 set to automatic, which is what I've read to be the correct way to go according to posts on this subreddit. I've even tried changing the resolution setting on the PS4 to just 1080p and just 2160p - YUV420. Neither of those changed anything.

I'm using the HDMI cable provided with the PS4 Pro.

I have enabled HDMI UHD Color on the hdmi input I'm using for the PS4. I even tried disabling that and nothing changed.

I have tried the YouTube app on my Xbox One, the YouTube app on my tv and YouTube in the web browser on my PS4 Pro and they all look like shit. Videos from the YouTube app on my Xbox one and OG PS4 looked great on my old 1080p TV.

Idk if 1080p upscaling is a thing on 4K TVs but if it is, is this possibly broken on my TV? Or is 1080p content supposed to look worse on a 4K TV? Or is it supposed to look the same?

Any help/input/suggestion of a better place to seek help would be greatly appreciated, thanks~

Submitted by p1zzaforbreakfast | #Specialdealer Special Offer Online Shopping Store 2016