Sigh.
First of all, no, there were not always just six teams. In fact, despite the “original six” name, the Bruins, Rangers, Blackhawks and Red Wings were not original franchises. There is precisely one original franchise; the Canadiens. You could argue the Leafs are, too, if you argue they are a continuation of the Toronto Arenas.
Secondly, let me repeat ymself; there was NO talent organization and identification system worth mentioning, and there was almost no organized hockey outside of Canada. The NHL had no Europeans and almost no Americans. Yes, the talent was concentrated in a handful of teams, but there wasn’t a lot of talent.
Georges Vezina was discovered when the Canadiens played an exhibition team against his team the Chicoutimi Hockey Club. They actually BEAT Montreal, shutting them out, and the Canadiens offered him a contract - which he initially refused, because he couldn’t be bothered to move to Montreal for a contract that even then wasn’t significantly different than what you’d make working in a factory.
Can that happen today? Well, of course not. It’s impossible. Imagine today’s Montreal Canadiens playing an exhibition match against some intercounty club, losing, and finding out the other team had some unknown goalie who was NHL calibre. It’s inconceivable.
In, say, 1930, there were more NHL calibre players in club and semi-pro hockey in Canada than there were in the NHL. I assure you that is not the case today - and now we draw not just from Canada, but from the USA, Finland, Russia, Sweden, Czech-land, et al.