Thats a very subjective question. It all depends on what you want bitcoin to be.
Do you want it to be an easy way to send money to people without a nanny (bank) looking over your shoulder, analyzing everything you do and sending a report to the government about your actions? Would you like to be able to send money around the world without paying an oppressive dictatorship (bank) for the privilege of doing it? Then dont change anything because bitcoin already does that.
Are you more interested in atomic swaps between cryptocurrencies? Then you need to support Lightning network development.
Do you primarily want bitcoin to be a vehicle for enhanced features like decentralized crowdfunding and distributed exchanges? Then you need to support projects like Omni Layer.
Do you have one specific requirement for your cryptocurrency like buying illegal drugs, guns, supporting terrorists, secretly paying prostitutes? Then you need to drop bitcoin and support altcoins like Monero.
Are you in love with your bank, your government and hate decentralization? Would you really like to modernize the banking system and help them speed up the oversight of your pathetic little life? Then you need to support Ripple.
Bitcoin can work for its originally intended purpose right now without any improvements.
When I first came to this forum there were no altcoins. I believe every time another altcoin is born it dilutes bitcoins user base slightly. You are asking me to give you something for free. You're not paying so you cant modify the rules. Maybe someone in the altcoin section will do the same thing someday. If you borrow my car for free instead of renting it you cant bitch because I wont let you smoke cigarettes in it.