The thing is, 5K displays are still a niche product area even after 5 years, so there's little competition. You only save a couple hundred $ buying an alternative to the Studio Display, which isn't worthwhile if you care at all about the built in accessories and the first-class TB support.
I think you've hit on the problem. Normally, an IT product that cost $1200 in 2016 would have been replaced by something with significantly better specs/higher resolution at the same price by now.
However, the PC market has hit 4k and stubbornly stopped. Problem is, 4k UHD is "good enough". Up to about 27", UHD is 'retina' at 21" viewing distance, so going higher brings rapidly diminishing returns. The Goldilocks Zone issue of 27" 4k screens needing non-integer scaling to get the system text/icon sizes 'just right' is a MacOS artefact that doesn't affect the Windows world. DisplayPort 1.4 adoption was slow, without which 5k needs Thunderbolt 3 or a dual-cable kludge.... So, basically, only Mac users want 5k and while HP, Dell etc. did briefly launch 5k displays they rapidly disappeared. The LG one was very obviously produced in partnership with Apple.
So it looks like there's no upgrade path for the "affordable" 5k display until mini LED comes along - and although the price of the Apple Studio Display seems high it could be that Apple, as the only user of 5k panels, are having to pay through the nose for the parts.
That's the problem though - with mini LED, maybe even micro LED and, hopefully, higher frame rates coming Real Soon Now and 5k looking like a dead-end format, $$$$ for an edge-lit 5k panel just doesn't feel like the investment it might have done 5 years ago.
Here are some of the ways the Studio Display is superior to the UltraFine 5K
...but the display improvements are fairly incremental, the sort of thing you'd expect "for free" from 5 years of progress, the cosmetic changes are... cosmetic, while the LG may have looked ugly it had better practical ergonomics (e.g. fully adjustable stand, built-in VESA mount as standard). I'm sure the new speaker system sounds better than
anything else built into an ultra-slim display but they're unlikely to replace, say, the
studio monitors and external microphones you might find in the
studio where you're going to use your
studio display. Heck, I only mess about with (alleged) "music" for my own amusement and use a $300 pair of KRKs (peanuts by monitor speaker standards) after experiencing the hot mess if you try even amateur mixing with less. Even enthusiastic YouTube vloggers are likely to invest in proper cameras, speakers and microphone gear.
Built in webcams are only good for video conferencing...and, looks like I might be able to use my iPad as a webcam for social Zoom meetings.
So whatever its features, I don't quite see who the Studio Display is
for...