> I remember something about Sublime being written in Python?

SublimeText is written in C++ with the "Skia Graphics Library" for the UI.

It exposes an Python API to extend the functionality via 3rd-party packages.

> I care about features the most, not if the app will open in 0.5s or 3s

Opening is not the only performance gain you will get for using a software written with native libraries.

You get faster overall operations in comparison with a program like GitKraken that needs to allocate several chunks of memory to execute simple tasks. It always baffles me when people use the startup time of a program as a mean to explain why they prefer using it over others. Electron-based applications are —overall— not performant. It's impossible to get good performance out of Electron because it sits on top of a web browser that is known to hug significant amount of memory from your entire system.

Sublime Text plugins are written in Python, but the core is C++ AFAIK.

I feel similarly and use VS Code, but GitKraken takes much longer than 3s to load on my desktop and it uses up to 500MB of RAM. Since I usually have it open with VS Code that's quite a lot of heaviness open at once. Then I've got several terminals open, a local Kubernetes environment, etc. Stuff adds up.