As a fairly committed Pokémon Go player, deep in the raiding community and playing the game daily, I was frustrated by the way that the EX Raid Beta was handled when it rolled out a few months ago. The only way to capture a Mewtwo in-game, the idea was that random gyms would be selected to house raids. If you happened to take part in a raid there in the days ahead of the Mewtwo raid, you would get an invite to take part. The idea being to encourage players to take part in raids at lots of different gyms, for a higher chance of facing Mewtwo.
The problem was, who got invited to raids was seemingly random. Players who raided at a specific gym on a daily basis would fail to receive invites, while others would get invites from gyms they hadn't visited in months. The seemingly random nature annoyed many players.
However, EX Raids are leaving their 'beta' phase soon, and the way they function is changing. There will now be two different ways to get invited to an EX raid for your chance to capture Mewtwo – being a frequent visitor of the selected gym with a high level badge there (regardless of how recently you've raided) should now sort you out, and people with a high rate of attending raids will also receive invites. It now seems to be taking your historical participation in raids into account, rather than just the days leading up to the EX Raids.
I hope this system works better, as Mewtwo is the only missing Pokémon in my Gen 1 Pokédex. I must have it! After spending £150 on Pokémon Go, it'd be nice to complete my Gen 1 collection at least.
— Pokémon GO (@PokemonGoApp) November 22, 2017
In related news, Pokémon Go players are one third of the way to seeing Farfetch'd available for capture worldwide.