As a retro gamer, it seems to me so limiting to not be able to play or enjoy games below thresholds that only current systems can reliably achieve.

I can't imagine not being able to go back and have a ball with F-Zero GX on Gamecube, Mario Galaxy on Wii, or Star Wars Battlefront on Xbox because they're sub-HD, much less not even being able to play PS3, 360, Wii U, or many Switch games cos they're 720p.

Lol, true xD

480P or 854x480 is 409,920 pixels.
720P or 1280x720 is 921,600 pixels.

If we keep both the same aspect ratios of 16:9 that is. 720P is just over twice the pixels of 480P.

16:9 480P was used on the WiiU gamepad and is used in many cheap low-end projectors and was even common in phones for a time.

Either-way... It places an importance of listing a whole resolution rather than "arbitrary" numbers like 480P if you are referring to anything other than 16:9 ratios.

High definition is relative.
Back in the 1990s high definition was a term used for anything higher than VGA resolution.
There will be a time in the future when they laugh at the poverty of 1080p resolution being considered high definition.

But in terms of our current terminology for video game consoles, 720p can be considered high definition, but perhaps not anymore for PC and VR gaming.

There was a time earlier this generation where consoles were getting lynched for having games that only ran at 720p, and that was 6-7 years ago now. Today, TVs are expected to have 1080p resolution, no matter what the size. Even 4K, while still more expensive, is now extremely affordable. I know that personally I cant stand watching most movies and TV shows below 1080p because it looks too blurry. As for gaming, it use to serve as my buffer for if a game I was playing was too demanding for my PC, but my current PC can run just about anything at 1080p with no problems. 720p really just feels obsolete now and I think its justifiable to not list it as HD anymore

For me 720p was never really HD, still those people you say in OP can still watch the 720p and below, YT calling that HD or not doesn`t change a single thing. Also 1440p isn`t HD it have some other letter before.

Seem like people are upset that a standard from like 20 years ago for what is HD or not would be changed. Technology have advanced so since 4k is becoming more standard on TVs and content is 1080p then 720p can`t really be considered High Definition anymore, and that doesn`t mean you can`t go back and play Pong on sub 200p and like it.

720p was never HD, it was enhanced definition (ED).

The original (XBox) 2001, was capable of outputting at 720p on select titles, and they were glorious.

That's a valid technical point. But a vast majority of SD TVs were not 16:9. Most content of the SD TV era wasn't designed for 16:9 either. Monitors during that period were generaly 4:3 as well.

In comparison, a vast a majority of HD TVs are 16:9. Hence, I went with 640x480 pixel count because it was common.

Honestly, that didn't really need explaining.

Some of the last CRT's were 16:9 widescreen and they weren't to bad... Although most were 720x480 "Enhanced Definition" and used a few tricks to stretch the image to 854x480.

Allot of Rear-Projection panels were the same.... Basically this was during the years just as we were starting to push towards Plasma/LCD panels.

480i however was in reference to 640x480 resolutions more often, although it is interlaced.

And you know me, I like a degree of accuracy in tech.

Not true.
720P is HD or "High Definition".
1080P is FHD or "Full High-Definition".

Enhanced Definition was progressive 480P and often represented resolutions like 720x480/854x480.