Someone said recently on the discord "Every Canadian plays US East", which applies to all unpopular regions. Everyone uses the closest of the 3 major servers: EU, AU and USE. It even applies to Europeans, who go visit the USE matchmaker when playing after 11pm! It means a lot of times, people from the same country end up matched on a faraway server, and it has been observed that their connection gets delayed in match even though they're physically close. I suppose it's because the traffic is getting diverted via this other region's broker (to avoid IP doxxing), while there is a much closer one that is unused.
I think once the match has been found, the broker that regulates the traffic should be selected as the closest one to the host, independently from the matchmaking region. This will allow players from unpopular regions to get matched with players from their regions and have decent ping for both of them.