Is it worth joining prop trading firm as a day trader?

Yes.  Trading today is no different than when Jesse Livermore traded stocks in the “bucket shops” of the early 1900’s.  He was able to beat them consistently even though they had every advantage.  He was able to out think them.  It can still be done today.

The most important aspect of trading is to understand that trading is all in your head.  It is not in the markets.  Your “playing field” is not your computer screen or chart, these are merely tools for you to accomplish the task.  Your “playing field” is your mind.  That is where the game is won or lost.  Most traders play “checkers” when the traders you are trading against are playing “chess” and are 3-4 moves ahead of your thinking.  If you want to beat them you need to start playing chess.

There are bots and algorithms in all trading now.  The human mind can out think any robot or bot they can build.