It's really not that difficult to understand. Realistically speaking, game changers does not have the talent pool to build a roster that could make it through to the challengers league. Even if it does, assembling that talent pool onto a single roster probably isn't possible.
If katsumi feels like she as an individual can aim higher(or if she just wants to try and quit if it isn't possible) and the only thing she is concerned about is making it to through to the challengers league and potentially ascension one day, then the best decision is to ditch game changers entirely and play on a co-ed roster.