I don't think there's necessarily anything bad about having a written constitution but only if you change it as time moves on. There are of course mechanisms within the US Constitution to add amendments (and use amendments to retract previous provisions of the Constitution) but, since 1971, no one seems to be willing to put forward an amendment for ratification. Which, compared to the rate at which they were proposed and ratified prior to 1971, is a very long time to go without a change (an amendment was ratified in 1992 but it had originally been proposed in the 1700s)!
On the Second Amendment people perhaps forget that when it was being written guns worked like this:
Rather than this:
I rather think if they'd known how guns were going to develop they'd have worded it differently...
And yet, these days because so many people and politicians (Republican's in particular) refuse to accept that perhaps the Founding Fathers included a mechanism to amend the constitution for the reason that time moves on nothing changes. The Second Amendment seems to be one of the most egregious examples but I'm sure there are other areas.