Your observation is why most people tell beginners (and sometimes intermediate players) to just follow opening principles: https://www.chess.com/blog/KeSetoKaiba/opening-principles-again
You can stick with the Italian Game if you like, but it is also important to learn what to do if your opponents do not play into the mainline(s). This is why understanding common plans and ideas of an opening can be useful; this way, when the opponent deviates, you are more likely to not be completely confused at what to do from there.
If you want to play the Vienna (or keep experimenting with the Italian) or not is up to you.
So i went to a chess club last week and they told me that the italian game would be a great opening for getting a clear game plan when you learn the lines. The only Problem is i now know the theory but i just never get it. I got the Elephant and Duras Gambit more often in the last week than the Italian Game, and thats no exaggeration. If i got to the italian game i got either the Rosseau Gambit or the Hungarian Defense. I feel like no one wants to play the main Line, which i am not blaming but it feels unpractical. Do you think its worth learning all of this stuff after Nf3 or would it also work to continue playing the vienna, which i played since now? It worked pretty well getting me to 1400 on chess.com.