P: I want to be able to exclude specific folders during synchronization

...just to clarify, I did state that the Import dialog and the Sync Folder have got different interfaces in themselves, but failed to mention that the latter can easily invoke the former.

So we then go to an Import ADD session, with the relevant source location already loaded up.

It's true that this lacks the ability to turn off "include photos in subfolders". Consequence: we declare what folders to include - not what folders to exclude. But we can still leave out the images of a given subfolder from inclusion.

If that top folder is highlighted then all of its direct and indirect contents are automatically included. regardless whether those subfolders are themselves highlighted or not. If that top containing folder is not highlighted though, then we can highlight just the subfolders we want to include.

But what about images directly inside the synced folder and not in any subfolder?  This is where it would be more convenient to have a "don't include subfolders" toggle control, to help us in selecting just what we actively do want to import. To be clear, this addition would help everyone not just those starting out from Sync Folder. 

Lacking such a checkbox, and if we want images from this synced folder as well as from only selected subfolders - one method would be to highlight just the subfolder(s) we want to exclude (so that we see only unwanted images). Uncheck All. Then click again on the parent folder so everything shows once more - but with all our unwanted images retaining their un-checked state. So an Import will then omit these.

IMO the observation that Import does give folder selectivity, and the desire to have folder selectivity under Sync Folder as well, are not in any kind of conflict. The Import dialog option is just a workaround not a full substitute - IF Sync Folder is the method through which the user wants to bring in extra images (something which nobody has criticised).

The Import dialog and the Sync Folder command have completely unrelated interfaces and capabilities at present. To equip Sync Folder with an entire new interface seems like a lot of work for the benefit of only those users with this particular use case. I've never seen this asked for before, so this is probably not a very widespread desire.

I would agree that some development of the means of browsing the file system - leaving the Folders panel aside, which derives only from the Catalog and designedly so - could improve everyone's experience not just those with this particular use case. I'm thinking of the precedent of how the identical Renaming Template options show both when importing, and when renaming already imported files.

If this more developed browser can indicate images already imported to this Catalog, also folders containing such, so much the better. And then it could be invoked from within the Folders panel for various purposes, and show up in the Import screen too, export destinations, print to file...

Took me w hile to understand what you were asking for but I think I get it now. I would actually contend that what we need is a real file browser within Classic that is more like Bridge or like the new local browser in Lightroom Cloudy (why just in Cloudy? We really want this in Classic!) with an easy option to add images to the catalog if needed. I'd agree that the folder synchronization option is too crude and there is very little custumization.

"Adobe will do what Adobe will do"

And they're more likely to do this if there's a clear rationale for it - not just a (somewhat entitled) "because I want it..."

Yeah, you do - you need to justify Adobe throwing money at it.

Short answer AFAICT is that you approach Adobe in the first instance by posting an Idea, which you have already done. Chasing up Adobe to implement your proposed change: I don't know of any end-user channel for doing that.

My understanding is that general Discussion posts are not systematically reviewed by Adobe staff. But there is some formal Adobe consideration for Ideas, as I understand it - and in this context the number of Upvotes by other users may add some weight.

How do I approach Adobe, then?

"and two people have suggested a procrustean approach; there's nothing wrong with the software but something wrong with me so I need to change."

I have not said anything about the merits of your feature request. Rather, I've encouraged you to provide more details about how it fits into your broader workflow, to make it more likely other users would vote on it and Adobe seriously consider it (as Adobe has stated in their "How to write a feature request").

Without such an understanding, other users and the Adobe product team are more likely to think the current features are adequate for their limited, probably mistaken conception of your workflow, and your feature request will end up in the bit bucket.

I think this thread has run its course.  As the OP obviously thinks this is a worthwhile feature (and some replies agree), then the OP should submit it to Adobe as a new feature request.  

It's also obvious that severl responders don't think Adobe will pay much attentuion to such a feature request for various reasons.  This is just an observation or prediction as they are not in Adobe's decision making loop.  Adobe will do what Adobe will do.  If such a feature request gets a lot of upvotes Adobe may pay more attention to it (or not).

At this point, I don't see that anything more can be gained by further debate or discussion on the topic in this thread.

I'm intrigued. I come here to request a change, and two people have suggested a procrustean approach; there's nothing wrong with the software but something wrong with me so I need to change. Cheerful response - I wouldn't waste my time thinking through the problem and then articulating it here if I was going to do something different, so perhaps we can leave that tack alone. I said in the very first posting that this was not to be a discussion on workflow and that is exactly what you are trying to make it. Can we get back to the matter in hand?