-To analogize, think of the iPhone in 08. To see the opportunity, you had to imagine 1) that weaknesses get mitigated (it gets faster, service gets better), and 2) entrepreneurs will take new features (like GPS) and create new ideas with them
For example, BTC's value is enabled its scarcity. This scarcity is ensured through the code and design of BTC itself. There isn't a central party that can change the rules on users and take the supply beyond 21m coins.
A very hard unsolved problem, in fact, is how to make it private. The idea of using it for money laundering is absurd. It's the worst way to do it. Everything is public and exposed.
-What is the main limitation today? Performance. A blockchain computer inherently takes a hit on performance, because the design is foundationally based on the idea of not trusting a single computer. You need to pay for the overhead of running all these computers