In late June early July Reddit was awash with people predicting a digg like doom for reddit. I got sick of commenting that 90% of reddit users wouldn't understand what was happening and 99% wouldn't care. Reddit was always going to "win" in that they would carry on, more profitable than before.
I don't know or care whether the reddit "experience" has diminished in either the short or the long term. I expect it has in some way, but it's more like a continuation of a long-standing trajectory.
In any case, as you say, the landscape has changed. Back in April lemmy was more or less non-viable to scratch that thread based news-aggregator itch. That's no longer the case.