Bitcoin never closes the opportunity to investors. It is the investors that miss the opportunity because of certain reasons like doubt, fund shortage and not trusting the Bitcoin market.
The party opens for everyone to join since 2009.
Bitcoin market is a free place for everyone to join from centralized exchanges to decentralized exchanges to OTC market. People can purchase bitcoins in many ways, KYC, no KYC, in person and many more ways. The barriers for people are only they don't have open-mind to learn a new technology and to see the self-destructive and self-devalued fiat currency and central bank systems.
If they see the fact, they will be more ready to join this market.