I think it is more fair to say that Bitcoin is no longer in the early adoption stage, as there are lots of new coins being developed and even some established coins are seeing radical overhauls in how they work (like Ethereum). Bitcoin has built a rather steady foundation for itself and will probably stay relatively similar into the future. Even the larger financial institutions are only just starting to branch into the smaller alternative cryptocurrencies so there is still a lot out there that is untapped. It is definitely a maturing industry that has had a lot of exposure in the media over the last few years, which is great for all of us, however there are elements of it that are still in the early stages.
I still think Bitcoin is in the early adoption stage, simply because not many people know about it. The vast majority of people worldwide still use Fiat for day-to-day payments. Crypto may have been widely successful since its inception, but it hasn't been able to challenge traditional payment processors directly. There are a lot of issues that are needed to be solved before crypto becomes a serious alternative to Fiat. Limited transaction capacity and high volatility is what's "killing" crypto anyways. Crypto has a long road ahead before it becomes mature enough for mainstream use. Just my opinion
