You must learn the rules to know when to break the rules.
Not really if you almost always play against bad players (as you should).
Many concepts that GTO has clarified have been understood intuitively by many old-school players.
Like the importance of suited cards pre-flop when playing deep, smaller continuation bets on many flops, and polarizing of river bets.
As others already have stated it can be good to learn the basics of GTO to know where the equilibrium solution for certain situations is.
But don't spend a lot of time studying if it takes time away from playing.
Instead, use the time to find a game with players that are so exploitable that you almost immediately see if they call or fold too much and if they
bluff too little or too much.
If you don't find players that do a lot of mistakes, change table.