No, there's approximately just as much technical and interesting content on Twitter as there used to be. Lots of people left, lots of different people joined.

It's just that this content is outnumbered some 100,000:1 now instead of the mere 1000:1 it used to be (ratios made up, but directionally correct.)

From my point of view, HN is trending in that same direction. It's just that the ratios aren't nearly as dramatic.

It's the ratio that counts the most. You seem to be implying TwiX is getting an increasingly bad ratio. That would imply, to me, an increasingly limited lifespan for encouraging quality.