There are many sports were world championships don't neccessarily include the best athletes. There are examples in team sports: Ice-Hockey (NHL playoffs during the WC), road cycling (limited nr. cyclists per country and not even the same nr. per team). Then there are solo sports: Time trial cycling (limited nr. per country), skiing (limited nr. per country)...
Not that far back in history pros were not allowed at the olympics.
So real World Championships can be held with the system people agree on and maybe even without the pros.

Oh and I forgot, that in some sports one country thinks that only its league is of any value. Check MLB

Good luck