Start Minecraft (Java Version) without a launcher?

In theory, could you start Minecraft without the Minecraft Launcher? That works (my own theory) when you look in the folder

C: \ Users \ username \ AppData \ Roaming \ .minecraft \ versions \ 1.16.3

goes (like here now e.g. 1.16.3) and then the jar file starts?

So not in your theory. Therefore the launcher doesn't just open the Java file

if you know how the launcher opens and uses the files in what sequence, you can easily program a "Quicklouncher" yourself

which is not worth it, so you no longer have access to multiplayer
and there would be many problems

together, yes, but definitely not profitable

It is possible but very complicated and rather not manageable for normal people without any experience