back in my day we only had one language. it was called ASSEMBLY. wanted to make the computer do something? you had to ask it yourself. and that worked JUST FINE
One project I worked on had 10 different languages. That was rough. But even your basic full stack web application is usually 5 languages: SQL, a backend language, HTML, CSS and JS. Usually some wheel reinventing frameworks thrown in for good measure. 5 languages is light these days.
The python code we inherited had some performance issues. One of the guys was like "we should rewrite this in Java".
Luckily the boss was not an insane person and shut that down. The issue was an entirely stupid "...and then we do one query per project" behavior that worked fine when the company was small but unsurprisingly started to suck as users created more projects.
Instead of a months long complete rewrite, we had a two hour "let's add profiling... Oh wow that's a lot of queries" session.
I would say that over a decade of my career was coming in as a freelancer to fix codebases where a couple of people tought they knew better than the previous ones and proceeded to add yet another very different block to a codebase already spaghetiffied by a couple such people.
Sometimes it was coding style, sometimes it was software design, sometimes it was even a different language.
I reckon thinking that just deploying one's EliteZ skills on top of an existing code base without actually refactoring the whole thing will make it better is a phase we all go through when we're still puppy-coders.
The XKCD Standards comic writ large. There are 17 competing standards. -> "Hey, we should make a standard to unite all these disparate standards." -> There are now 18 competing standards.
How to go from only being able to compile the project on a Windows machine (due to obscure dependencies that every other Java project has for some reason) to not being able to compile on anyone's machine at all in just 1 simple step.