To make a perfectly secure piece of software it must be flawless. An attacker on the other hand only needs to find a single exploit, a single oversight, to break it.
Defending something is orders of magnitude more difficult than attacking something for that reason.
Over time defense will keep improving , attack on the other hand will become more difficult when common issues are no longer a problem ( say memory safety or SQL injection) when best practices become the norm.
In that HN thread you talked about someone had mentioned till sometime back even the official docs used to have examples with SQLi, which of course they don't anymore, making it slightly harder for junior devs to make those mistakes, each step is improvement.
I am not saying they already solved, I am saying it becomes harder to hack with some techniques over time as defenses become more standard and best practices become actually common place.