I have 2 on my island so yes there are some 25 player KDs out there of course...and in no way am I saying they xlog to succeed but many sit for provinces until they fill up.
But you see the argument is that new kingdom production is being stagnated by older/established kingdoms' quest for 25 players...often kicking the same amount of people they recruit in the same age. Those guys end up joining another KDs in which that KD turns over other people who also suck/retire.
If the game stops adding random at 20, then max KD size should be 20...or else all has done is force newer KDs to compete for quality players...which will always be one-sided fight. If established KDs need players they should be able to have random players join and share the same pain that most of the server have to face.