There has to be a middle ground between "Nobody should derive any confidence from the language a product is written in" and "I only use products written in lang

There has to be a middle ground between "Nobody should derive any confidence from the language a product is written in" and "I only use products written in language X". You shouldn't dervive all confidence in a product from it's implementation language, but when you are looking at all available products and need to filter down to ones you might be interested in. Implementation language can be a useful litmus test for understanding how it might behave without doing a complete in depth evaluation. For example if I learn that a desktop application is written in javascript, it is likely to be using electron or an OS webview. Or if an application is written in C++ it is unlikely to have GC pauses cause stuttery UI. Both of those assumptions may not be true (Sciter for JS and Boehm GC for C++ respectively). However those assumptions are a useful starting point unless proven otherwise.