> Especially for people who have never attempted to write the software they are criticizing.

E.g. Casey and Blow often criticise the Visual Studio debugger. It's slow, has quite limited functionality. And it progressively gets worse over time (e.g. it can no longer update watched values at the same speed as you step through the program).

Do they both have to write a debugger to demonstrate how bad it is?

No. Other people do it, single-handedly. See RAD Debugger (https://github.com/EpicGamesExt/raddebugger) and RemedyBG (https://remedybg.handmade.network). Relevant Casey rant: https://www.youtube.com/watch?v=GC-0tCy4P1U

And the same is true for a lot of other software.

You don't have to write some software to criticise how bad it is. E.g. I cannot but make fun of Discord for implementing "we will intentionally kill our app if it consumes 4GB of memory and are very good at prioritising fixing memory issues seeing a whopping 5% improvement for p95 of users": https://www.reddit.com/r/discordapp/comments/1pej7l7/restart...

Doesn't mean I have to write Discord to criticise it. All I need is an understanding of rather basic performance and of general engineering practices.

And also, you've probably failed to even understand what they are criticising/saying: https://news.ycombinator.com/item?id=46315616