Its a technique thats less demanding than running 1500p is, that beats base resolutions of upto 1800p.
Thats not a "backwards step" thats a technology that allows a console to punch above its weight.

Also sure 4k is the best.... but what if in this game, its too demanding to be realistic?
The PC with a 2080 ti struggles to keep above 60 fps in this game, at 4k.

That's pretty much where I'm at, and likely will be for a few years more. 1440p 144hz is just too good of a sweet spot for me to pass up. I'll probably go for 4k, when 4k OLED monitors are cheap and do 144hz. 

I'm going to buy a 4K HDR Monitor mainly just for content consumption. And maybe single player games but even then I'll probably stick to my 1440p 144hz. 

But Video content isn't really made for 1440p, and I doubt the PS5 will be able to send a 4K signal to a 1440p monitor because reasons. Sigh.

I just refuse to use 1080p after looking at higher it genuinely look 'blurry' in comparison. 

We may end with a mess that PS5 sends a supersampled 1080p image to your 1440p monitor and it upscale.

It look better with checkerboarding instead on native 4K

This is why 4k it's a waste of power, hell even PC now optimizing with DLSS and temporal  reconstruction.

PS4 pro started it and many people underestimate it LMAO. Now they understand that Cernies is truly Genius 

Like I said before the 8th generation even started and everyone was praising 1080P as the second coming of christ...
Resolution is one of the first key sacrifices developers will take in order to bolster image quality as it is a easy way to gain a significant amount of render time with minimal effort.

Frame reconstruction was thus the logical choice to make up for that... Especially as 4k started to gain traction. (Again, if PC can't do something, neither can consoles.)

There are many examples of other games where checkerboard artifacts does result in a significant regression in image quality. (I.E. Frostbite powered titles.) So it really does come down to developer competence, but we are at that point where developers have had years of exposure and trial and error and thus making some solid implementations now.

I am not going to chalk this all up to Cerny because the entire industry was working towards this end, they collaborated with AMD on checkerboard rendering, they didn't invent the technology as it's a hardware solution and AMD protects it's I.P.
nVidia pushed DLSS.
Microsoft with DirectML.
AMD with Radeon Image Sharpening.

Even Doom from 1993 (I.E. Super Nintendo era) had a form of image reconstruction where the game would render alternating pixel columns in it's low-resolution mode.

In saying that... I would still opt for a native 4k image over a reconstructed one.
But I would also opt for a 1440P image with 120hz and higher visual effects, resolution is only part of the graphics puzzle.

Lastly, I feel like you have missed the key points in the DF video and misconstrued their statements.

Yup , but none of them brought it up until PS4 pro came in. 

It's like how we forgot, that Technology are invented by smart people but mainstream help market adoption . That's the rule of thumb of every technological advancement.

I am not saying It's have not yet been implemented, ( also Checkerboard on PS4 pro is unique on it's way ) and Yes AMD has one with image sharpening, Nvidia with Dlss , and Microsoft with ML , but then again this never talked about until PS4 pro came in all of the GPU were not supported until the new one and no games on PC supported except  " a very few of them " , and how with cheaper solution will help RT on GPU, More Geometry complex , or better performance. 

Doom from 1993 arguably was the precursor to checkerboard rendering as checkerboard builds upon those same concepts from 27 years ago.

Checkerboard rendering is done in hardware on the Playstation 4 Pro.
The Playstation 4, Xbox, Switch and PC don't... They have to take a software approach, which is still effective, but does cost a little extra overhead... Some games on the Playstation 4 Pro likely aren't leveraging the dedicated hardware for the task as it might not be worth the development time for a developer to implement that tech for just one console. (And not even the best selling one in that console lineup either!)

DLSS became a  "need" due to Ray Tracing, before the PC could just brute force it's way, but hardware Ray Tracing puts a whole new pressure on hardware... And I would argue DLSS is still not needed on PC if you aren't using Ray Tracing.

Once the PC advances over the next few years especially once nVidia and AMD get a handle on Ray Tracing, the need for DLSS and image reconstruction will obviously lessen, the PC constantly improves and advances, consoles don't.

Even the PS2 had a few games (I.E. Grand Turismo 4) which operated at "1080i" which used various forms of upscaling to achieve that resolution output, up-scaling lower resolution games is an old approach, mostly out of need.

Again, never said it's never been done before, but  " thanks to PS4 pro : that made in to  " mainstream " now GPU and many games will adopt on the future.