Security is not binary. Security is not absolute. There is ALWAYS residual risk. There is no such thing as invulnerability or immortality. Everything can be taken down. Security is not an end state. It is an ongoing process.
If you do not continually improve the security of software, by addressing known vulnerabilities, performing a sane risk assessment, identifying threats, and doing what you can to mitigate them, you will regret it. The notion that implementing fixes is pointless because there will always be more vulnerabilities is wrong. Yes, there will always be vulnerabilities. Yes, security is a job that never ends. No, you can't ignore vulnerabilities once you know of them.