Security needs to be improved for the usability of bitcoin. Security needs in terms of transactions.
There is already enough security for transactions by the mining process. It is a core process of bitcoin and it is what keep the network safe from attacks.
There are some people also being hacked and loses their bitcoin holdings.
Almost always the fault lies at the end of the victim, not a problem with bitcoin or its use. If someone downloads unsoliticied email attachments and runs them without checking, leaves coins on exchanges and uses same passwords on different sites then nobody can save their coins from being stolen.
With a safe and secure wallets, people will become at ease and will not worry about their bitcoins on their wallets.
Wallets dont give security. The user has to secure their devices and leave no loose ends.
Also, faster transactions are the also one factor need to the improvement of usability of bitcoin.
Looks like you have not been up to date with lightning network developments.