FSS is not intuitive but once I grasp how to distinguish between bodies and USS frequencies or waves, I can fully scan an unexplored system faster than ADS. Prior to FSS, I will not SC to a body > 9,999ls away even though it's a HMC or higher value.
I believe FSS can be improved to filter on body and/or USS scan. Perhaps this will make it easier for others who dislike it.
I've been using the FSS Scanner Screen quite a bit in the bubble, usually while doing passenger missions to tourist destinations - I'll scan the systems I travel through & possibly map anything nearby to the destination for extra BGS points. But because I am able to target the [unexplored] bodies I can fly to a safe position out of the system plane to perform the scan without the main star blocking half the system.
With targetable, [unexplored] bodies the FSS works well and risks & inconvenient positioning can be mitigated, the workflow makes sense.
For USSs generally I don't resolve them in the FSS Scanner Screen, although if I feel I am safe to do so I may zero the throttle once I'm well clear of the entry star and quickly resolve a few. I am always in a hurry to complete the FSS Scanner Screen Sweep, but I am able to assess the risk and make a decision whether to use the FSS or do flybys. It works.
Out in virgin systems the vulnerability of being stationary in supercruise is reduced compared to populated space, but the frustration of which direction to fly and how far to travel before stopping comes to the fore. I regularly find myself having to exit the FSS Scanner Screen to move the ship to another location so I can scan bodies blocked by the star. Having nearby bodies that auto-scan really helps here, because it gives me an idea of the system plane so I can put the ship in a convenient location when I enter the FSS Scanner Screen. I always honk before entering the FSS Scanner Screen, for the FSS Scanner screen to require a honk on entry (if you haven't yet done one that session) is pure waste of time imo. If you log off part way through scanning a system it requires a fresh honk too, which doesn't make much sense to me.
There are a number of design issues with the FSS that having an ADS on board mitigates, and adding extra game rules that disable functionality of either when both are equipped would add needless complexity to an otherwise simple solution (use either or both a circumstances & mood demands, both have strengths & weaknesses). Having the sysmap reveal only black bodies wouldn't matter either way for example, but wouldn't help and still leaves us with the core issue of needlessly removing existing stuff several years too late.
What I am describing is already in the game in pre-tagged or pre-populated systems, and requires minimal investigation because it is just re-inserting well established, mature game rules (how the ADS works).
Then instead of 'we tried to accommodate everyone' FDev can simply say 'it is better for all', which is a win they sorely need imo.