I don't really know what your point is.
This game mode is to encourage and reward development. If that is development over time, or quickly via big spending doesn't really matter.
As players are able to fill the defence slots effectively, and still score more banners than their opponents on attack, they get more skill points, and they will get promoted.
At some point they will reach a league where they cannot effectively fill the defence and still attack well enough compared to the players around them. Then they will lose. If they lose enough they will get demoted to where their roster (and use of it) is effective again.
In kyber it is a bit different, because you have reached the point where you don't need to place more teams as you move up. Just the quality of teams needs to improve.
GAC is a game mode that consists of strategy and tactics. Strategy being how your resources are used to get the teams you need and setting up a team to succeed through team selection and modding. Tactics being where you put them on the table, and what buttons you push/targets you select during a battle. The skill rating comes from both your strategy and your tactics.
It will not always be fair. It just can't always be fair. Some people's strategy will have been so much better than others that the tactics hardly matter. Some people's strategy falls short in one area, perhaps mods for example, that the rest of their strategy or tactics cannot overcome. Some people's tactics are bad. The greatest tactician will not win if their strategy does not enable them to employ the tactics they want. Sometimes a plain old mistake is made, be it fat fingers or brain fade. . In all of these cases skill points will go up or down based on performance.
If you are seeing players that appear overwhelming, then either, we'll done you must be awesome, or they are terrible/inactive. An inactive player suddenly going active is a pain, and maybe that needs looking at by the developers. But it does not mean the entire system is broken.
I have played a long time and I vastly prefer this performance based system over the developers trying to create matches via some algorithm. They have proven many times over that they cannot do that very well.
