Replay groups are finally here ! This is only the first iteration: more features/stats coming soon(ish) !
Replay groups are only useful for game series, with the same set of players,
RLCS games for example.
Creating a group with all your 2v2 solo queue games for example will not give you much insight.
There will be another feature for this use case, i.e. seeing how you did/your progression in the last couple of games.