I'm just an outsider, but to OP's point, in 2017 they had none of what you just cited yet they were making the "within a year" claims, and continued to do so year after year. One can't help but draw a comparison to the boy who cried wolf.
Edit: This isn't me taking a position, just observing.
I'm also skeptical, but let's remember that the point of the fable is not "the boy's repeated claims lost credibility because the wolf never came", but rather "the people eventually learned to ignore the boy's claims and were caught by surprise when the wolf finally came" ツ
But if PoS comes after everyone stops caring about ETH (or PoS), it still fails. PoS isn't the hard part. Getting ETH successfully onto PoS is the hard part.
According to the people designing and building this stuff, PoS itself was a lot harder than merging it with the rest of the network.
For PoS there was all sorts of complicated game theory, a whole new protocol, and trying to figure out every possible way to attack it.
For the merge, it's basically just changing the fork choice rule of the existing network, so instead of going with the fork with the most work, it goes with the one being chosen by the PoS network.
Edit: This isn't me taking a position, just observing.