Unless your somehow naturally amazing at the game, by the time you get to that point you'll surely have decently leveled brawlers FTP or not. At 17k, most of my brawlers are at 8 or higher (granted I do try to maximise progression and spend my gems wisely).

But even if you don't have high levelled brawlers it's still totally possible to win if you are more skilled then your opponents. Level 1 trophy records are broken frequently. There are people with level 1 brawlers in the 800+ range and soon, as crazy as it seems, im sure we'll see our first level 1 rank 35.

The reason why people like OP feel like they've hit a wall is because skill cap for Brawl Stars looks wayyyy lower then it actually is. Although it's far less complex then most other MOBA's, there's still a suprising amount of stratergy and synergy to be understood and perfected.