I would say your “more or less disappeared” must really mean, “aren’t mentioned in gun mags any more...”
WSM’s are still kicking around. Might not be making the headlines in hunting magazines, but there’s still ammo on the shelves, still rifles, still brass (actually better supply for WSM brass today than there was 5-10yrs ago).
Ruger Compact Mags and the RSAUM’s are still kicking around as well. The 416Remington never has been mainstream, it’s still around, even feeding an incredibly niche application - replace “Remington” with Rigby, and the statement remains true. 404 Jeffery just made a bit of a resurgence after around 50yrs of near-obscurity. The .458win Mag has enjoyed continuous life, despite being a very low volume and variable popularity cartridge. The 6.5 Grendel is doing better today than any time in a decade before, despite overwhelmingly bad market launch strategy by Bill Alexander. The 6.8spc is still enjoying blood flow despite being overshadowed in the firearms advertising media by the 300blk while it was still in adolescence - which has already itself been overshadowed by the 22 Nosler and 224 Valkyrie. The 6mm Dasher is more popular today than any time in the last 15yrs at least. The 260remington was floundering around in “whocaresville” for decades before the 6.5 Creedmoor shined a spotlight on its cartridge class... how popular would you consider the 17 Remington, 22 Hornet, 7 Dakota, 30-378 Weatherby, 257 Roberts, 7-30 waters, 7 Mauser, 221 Fireball, 17 Mach IV, 30-40 Krag, 32 Special, or any of a thousand other cartridges which can be found in production for ammo or brass, but which don’t draw much market popularity or gun magazine/online forum fanfare?
There’s a wide chasm between the second most popular cartridge in the world (5.56/223) and complete obscurity. A friend messaged me today about a Winchester 71 in 348winchester - only two models of rifle were ever chambered for it, one of which was almost cartridge exclusive, and production halted 60 years ago, and only 3 factory loads were made even when it was in production. An obscure rifle in an obscure cartridge of an obscure caliber, but brass, bullets, and dies remain readily available to keep a rifle well fed...
So when you say “disappear,” it tends to make a guy think it can’t be found - whereas any of these new cartridges haven’t “disappeared”.