If you're relying on straight pieces you're doing it wrong!
Back when I was starting with Tetris I would always try to avoid "holes", i.e. empty spaces that are covered on top. And this leads to the requirement for the straight pieces.
I became much better when I started to accept holes and instead just try to keep the top edge a nice shape compatible with many blocks. The straight pieces become a bit of a nuisance, actually.
I think you take a major strategic step when you force yourself to use the straight pieces horizontally. You learn how to play without relying on them to clear large areas.
Back when I was starting with Tetris I would always try to avoid "holes", i.e. empty spaces that are covered on top. And this leads to the requirement for the straight pieces.
I became much better when I started to accept holes and instead just try to keep the top edge a nice shape compatible with many blocks. The straight pieces become a bit of a nuisance, actually.