Self policing doesn’t work, hence the standard of behaviour is so poor now
Policing onkh works if umpires are strong, willing to report players without exception and the league back them up with harsh punishments..
Clubs will only sort it out when they lose players to bans for weeks.. capt will only policemit when they lose players and get banned themselves.
Umpires talk pre season about doing it but never follow through
The line of authority goes from league -> club committee -> captain-> player.
If the player steps out of line, the club disciplines him, if the club steps out of line (including failing to control its players), then the league disciplines the club. The captain is obviously at the front line in controlling his players, if he can't do that, the committee need to find someone who can.
The problem is that leagues don't do enough to bring sanctions agaisnt clubs. If they did, then clubs would crack down on their players's behaviour.
Umpires are a red herring, 90% of amateur games are played without independent umpires. If there are umpires, great, they should report every instance of poor sportsmanship they see. But in most cases it has to be the clubs themselves who do the reporting to the league.