The point isn’t that there are multiple ways to get a gun, it’s more that there are a lot of ways to kill people and advances in technology and dissemination of information is going to bring more of them within reach of the average homicidal person.
I used to be mildly frustrated that my civil rights were being eroded but it was largely an abstract issue. Now, I increasingly wonder how we're going to cope with significantly more accessible and capable technology. It doesn't seem like anyone is putting much effort into discovering or addressing the underlying causes from where I'm standing; I don't see how this can end well.
I don't buy this.
The "average" homicidal person generally isn't that capable. And everything you mentioned requires at least above average skill levels in quite a few different areas.
Yes, a smart homicidal maniac may have a lot more options, but most homicidal people simply aren't that smart.