In my game everyone stumbled around for about 10 rounds rolling initiative manually using the modifiers for wepon speed, casting time etc.... In addition to that, I have initiative order hidden so I ask players to roll their initiatives in the tower. We're all pretty fluent now after only a few combats. The DM IMO has it the worst with every NPC needing to be adjusted for not their size modifier but the weapon or spell speed. Even that you can get pretty fluent pretty quickly I found. I believe there might be a QoL adjustment coming in the future to this.