Actually I doubt you "always" played and I assume this is just recently and yea from now on nothing will change if they don't unite more servers.
First of all you are wrong from the start because there are not millions of players. The game is divided in dozens if not 100-200 servers and if you will do a simple math you will see that from dozens of millions you will end only with a bunch of teams.
Let's take 100M accounts on 100M servers, you will end from the start with only 1M players on your servers but remember your server didn't started with this huge number of teams but with much less, only 7 teams promote per season, after 34 seasons how many teams do you think will remain at that level? I told you, less then 100, just a hand of teams and you always play with those with closer quality like you.
Nothing special, there's just lack of teams. Ask anyone who's at the highest level on his server or closer, you will see and they can confirm that they have same opponents over and over again.
Don't fool yourself at your level there are not millions of teams, just a hand of team.
The only thing you can do is to trick the system, change your quality (less or more) and maybe by luck you can get other opponents or just wait until the developers will unite your server with another one.
Just to prove isn't just at you and you are wrong, is quite same at me, especially after level 30...
LEVEL 31
LEVEL 32
As you can see: club pizza, that guy with weird name and black emblem, gsred, steaua ploiesti, etc.
EDIT: Check level 30
And as you can see, none of them are on my friends list.
The only thing you proved is that there are just few teams left at your level on your server. Sorry to say that but that's the truth, very simple.