Most of the regular Crucible modes in Destiny 2 no longer have skill-based matchmaking as Bungie decided to focus on improving the experience in other areas.
Bungie is doing away with skill-based matchmaking for most Crucible modes as it apparently made the experience less enjoyable. Some of the cited reasons are longer queue times and potential lag. The new matchmaking is supposed to be connection-based so we should technically have fewer lag glitches where we keep shooting a Guardian and nothing happens.
Similarly, this should help with hit registration but it remains to be seen how the system will work in reality. For example, the TWAB mentioned that queue times should be lower now but we didn't experience a noticeable difference so far.
The matchmaking change has been applied to all playlist except for Elimination, Survival and Survival: Freelance. These modes will continue with skill-based matchmaking due to the players fighting for Glory as opposed to Valor resets.
Similarly, Trials of Osiris will continue to use card-based matchmaking so you rewards will not merely depend on whether you will be queued up with strong players who have connection similar to yours.
According to the TWAB , Bungie are aiming to make Crucible more appealing to casual players as it is now supposed to be a mode "where the outcome of the match isn't as important as enjoying the experience".
Additionally, they are looking to "play into the strengths of Crucible being a bombastic, frenetic action game". That description might fit Rumble well but considering Control has more depth built into the objectives, it's hard to imagine someone is going in for "frenetic action" instead of an objective-based mode.