GC exists as a safe space for female players. But GC teams have a chance to play in challengers like every other team, they have to play through the open qualifiers and try to qualify for Stage 1. For example, Shopify/V1 played in open qualifiers this year and last year (I think) and got destroyed by essentially low Tier 2 teams and ranked players, which shows the gap between the GC and Challengers.
As for if they have a chance to play in Tier 1, it's possible, but the problem there is that 99.9% of Tier 1 (likely even Tier 2) won't pick them up. It's not a gender thing, it's mainly because there are better players (skill-wise) to pick up than a GC player (no offense).