For some reason they changed the number of league in each Tier.
So Platinum was the top 20 leagues from the last brawl, gold was the 21-40 etc etc.
I don't know exactly how many it is now but it seems in the order of 100 leagues get put in Plarium. That means the majority of active leagues are placed in the the same tier.
This did get brought up when it was changed but it seems to be something Plarium don't want to change. Possibly it was about the number of sapphires being given away for relatively low performance (but they could have fixed that by simply changing or removing the level of sapphires in lower tiers without dumping everyone in one tier - which creates other problems).
One thing I will say is that despite everyone being in the same tier, the matching mechanic is skewed in some way so that the top leagues always get the top leagues in the individual match up's, it's not random across the whole set of Platinum leagues.
I know that doesn't fix all your problems but at least it means in the individual match ups, you shouldn't be continually put up against ppl you can't compete against over and over again (you'll get some bad match ups though).
And yeah, to the second post people still do the intentional "yoyoing" between tiers to farm sapphires. So the really samll/new leagues in gold never have a chance of winning because big leagues are intentionally getting demoted to gold each week. They need to expand it further than just last week's performance to maybe an average of last 3-4 events if they want to fix that.