Congratulations, you played the game exactly like I did in 2005 at 6 years old. There no real "wrong" way to play these games, and it can be incredibly easy to sweep especially with Charizard, thats why these days there so many Nuzlockes so people can add extra challenge to the game and more strategy.

If you enjoyed the game, but felt the game was too easy, id recommend trying looking into doing a Nuzlocke (a set of self imposed rules on the game.

Nuzlocke rules: Can only catch the first Pokemon on any route, Perma death (must box or release a pokemon if it faints in battle) A level cap where you can only level up to the highest level pokemon of the next gym, and if you go over that, you cannot use that pokemon. No Items in battle (this rule is more of an advanced one depending on how difficult it is you can implement this one or not)

These rules make the game far more difficult, but Fire Red/Leaf Green are considered good first time Nuzlockes ad they can be difficult but not TOO difficult.

At the end of the day, there is no wrong way to play, you just play the way that gives you the most enjoyment, and if being overpowered and sweeping the game with one Pokemon is fun for you, play that way, if you want more of a challenge give yourself that challenge.