“Scenes” mean many different things to many people - it’s a widely used term in different systems and often with different concepts. I’d agree with most of the comments above - Rules are the way to manage scenes in OH and should allow you to do most things.
While I fully agree that there are many things that can be done now with the power of rules, and this is certainly the preferred and obvious way to implement “scenes” - there’s some that can’t be done - or at least can’t be done well. Unfortunately, groups / scenes is one area that falls down in OH since we can’t group items together into groups that bindings have visibility of.
Why is this important? Well, often when you set a scene, you want to set a bunch of lights to the same level - possibly with other actuators such as lowering the blinds so that your TV room is as you want it. At the moment, this is either done as a rule, or a group item. Either way, the binding gets a bunch of separate commands coming in - with lights, this becomes very noticeable as 12 different lights in a room change - each 50ms after the other.
Many systems such as ZigBee (and all the systems that use ZigBee such as Hue, Ikea, etc…) and ZWave, and I think KNX and no doubt many others have methods to work around this by communicating to multiple devices at once (ie multicast), but it’s not really possible to use this in OH as the binding doesn’t know that the user wants to control a group.
So there are things that can be done now - much/most/all of what people want can be done with rules for sure, but there is certainly room for improvement in the user experience. Unfortunately though, I don’t think OH3 is likely to see any significant changes to the concepts we’ve had in OH1 and OH2 .