Worst GAC matchup ive seen yet!!!!

It isn't as simple as a margin of difference within each metric.  First you have to define what is an acceptable difference for each metric, and which metrics do you consider? Also, what weight do you give to each metric?

For example, when I pull up my GAC bracket on swgoh.gg it lists a LOT of metrics.  GP, zetas, omicrons, GLs, Relic Units, G12 units and that is just the summary.  You also have to factor in relics, mods and datacrons.  and there are a WHOLE lot of details in there.  You and I could have the same number of 6 Pip mods, but I may have a lot more mods with higher speed stats.

Then there is that matter of which legendary characters do you have vs your opponent. Is it a fair fight if your characters are better, but you have trash ships and I have really good ships?

You will never have a "fair" match up every time.

The way it is is not perfect, but it is actually pretty good and far better than it used to be.