Um, you are blowing up a 1920x1080 image to 3840x2160. The individual frames of a video are not vector graphics. It loses quality when you blow them up. I have seen it. Just take a simple AE project, produce it at 1080p, then go back and blow it up. I can tell the difference. It does not look as crisp and as good as the 1080p one did. Just like when I watch 1080p footage full screen on my 2560x1440 monitors, it looks worse than on a native 1080p display because it is blown up. You cannot gain image data just by blowing up the image. If you can, why not just take raw 720p footage and blow it up to 16K? It WILL NOT look crisp.
I have tried it. I upscaled one of my title sequences from 1080p to 4K and it looked HORRIBLE at 4K because....it did not magically generate extra pixel color information for the 4x resolution increase.
This is like saying "Generate a 100x100 image in Photoshop. Now blow it up to 200x200. SEE how it MAGICALLY gained those extra pixels and color data?" No, you blow up an image higher than it's original size it looks bad. 100x100 vector image CAN be blown up to 10,000x10,000 and look crisp.
Well all I have is Spectrum internet, so that is probably why it sucks for me. But I cannot expect my clients to download a 4K video because it does not benefit them AT ALL. and I get massive requests to even serve videos at 720p due to our crappy internet in our country.
I think you're fundamentally misunderstanding everything there is about resolution and image quality. Haha. Nobody EVER said the image magically becomes higher resolution when you upscale it. You're making that up. Nobody said that.
Also, upscaling an image does NOT make the image look worse. That's 100% false. Upscaling doesn't change the way the image looks at all. The footage will look exactly the same. 1080p will not look "worse" when being upscaled. BUT, it WILL receive LESS visual compression when being uploaded to sites like YouTube. This is a FACT. Higher resolutions don't suffer from visual artifacting upon compression as much as lower resolutions do. You don't have to agree with the facts, but they're still facts. If this weren't the case, then why do major film studios upscale their 2K films to 4K for consumer delivery on platforms such as Vudu and 4K UHD Blu-ray? ANSWER: Because those delivery platforms are compressed, and higher resolutions react to compression better than lower resolutions.
No one's saying that you have to deliver in 4K to your clients, so you can shut up about your clients. No one cares. Keep delivering in 720p. Go for it.
But you can't go around telling people crap that's not true. Upscaling IS a very normal and common way to combat compression. IT JUST IS. Deal with it.