Ever since I started working with merchants accepting Bitcoin, all the way back in 2011, I've watched the industry go through drastic changes.
In the early days there was a wide-eyed naive enthusiasm about Bitcoin, rooted in a political need for financial freedom. A lot of the early adopters of Bitcoin were Libertarians. They viewed bitcoin as a way to unshackle themselves from the tyranny governments can impose through financial control.
To become fully free of the old financial system... and to see as much of a profit as possible, the entire world was going to need to get on the Bitcoin hype train.
There was a vision of a world where Bitcoin replaced credit cards. Individuals would swipe their phones at Starbucks (which has happened to a degree) while credit card readers gathered dust. Everyone and their grandmother would have a Bitcoin wallet.
That obviously didn't happen.
It didn't happen because the blocks were too small, or that transactions were too slow. It comes down to simple human psychology. People are lazy. There is simply no reason a consumer would switch from their perfectly working credit or debit card to a new platform which isn't universally accepted.
Cards work. They know how to swipe a magnetic card. Sure there's identity theft, but the bank normally fixes that. There's no huge downside and everyone's 'happy enough'.
The marginal % in savings by using Bitcoin just isn't enough to convince consumers to switch.
But I think a lot of that original naivety in Bitcoin is gone. Bitcoin companies have focused on either servicing needs internal to the Bitcoin community (hardware, mining, etc.), focused on niches where credit cards don't work (gambling, adult, international), or left the Bitcoin community entirely(Circle's pivot comes to mind.)
There still seems to be some hope and optimism in developing markets that Bitcoin can be used instead of plastic cards. I think the startups looking to create a mainstream consumer-centric business model in other countries, or even worse, using random altcoins, will face great challenges and be forced to pivot or close.
I think a lot of the unknown growth potential of Bitcoin has been spent. People know the areas where Bitcoin will be useful in the future, and now, the growth that is coming (at least in the U.S.) is not a bubble, but reasoned, rational investment, in a financial instrument which is filling a great number of use cases.