Must have missed the Caulifla thing then.
Frieza becoming that powerful in that short time span is shytty writing, but is unavoidable due to the constraints the anime already put on the manga. But they at least mentioned Frieza doing some training in space. 17 just somehow magically got stronger while being a park ranger?
No, that's good writing. The anime fukked up bloating their power levels to an unnecessary extent. Nothing they did was even central to the plot in anime. Get rid of the useless characters.
They said 17 was training all those years after the Cell Games, that's a longer time than Freeza.
The main plot was for the team to eliminate everyone else. By giving them wins they are serving the main plot. There is no point in creating useless characters.