You could even argue capitalism itself is still an ongoing experiment
Right now, it's not going too well in fact, with an ever increasing gap between poor and rich.
We're going a little off topic here, but I'd argue the other one called "communism" is an ongoing experiment with several countries, and almost all of them I would consider to have failed already. The fact that there are poor and rich in capitalist countries reflects on either the people or the circumstances of the people, not the government or the businesses. Lot's of self-made millionaires were born into poor families. Lots of people born rich are now poor. It goes both ways.
I agree; also did not want to go off-topic, just show that almost anything can be called experimental basically...
It's hard to define or say if something's 'not experimental anymore'.
I think only mass adoption would make it non-experimental.
Even then, you could argue it's still an ongoing experiment (like literally capitalism and communism themselves; both are mass adopted and in a way still experimental).
Let me explain: every time a milestone is reached, like 'legal tender', 'mass adoption', 'global reserve currency', ..., the circumstances are completely changed and we're in a new kind of experiment. For example, let's say
BTC exited 'experimental' status in El Salvador and it is mass adopted globally, it'll be again experimental, because it's a whole different situation, economy, size, scale, political system and landscape; so it'll be 'experimental' again and it's not guaranteed that it will work globally the exact same way it works in El Salvador.