Eh, as I always say, Frontier could do better than both the FSS or the ADS. It doesn't seem like they want to, though - at least, certainly not for Beyond Chapter Four and since. Checkboxes ticked, good enough, move on to the next thing.
However, one problem is that of longevity. Try asking around, talk with explorers who started after the FSS (so they aren't "tainted" by what was before), see what their opinions of it are. Sure, those who only explored a few thousand systems in the two years since might still be content with it, but from those who explore(d) more actively, the response is often that it's an unenjoyable grind.
Or hey, try looking at guides about getting materials from signal sources and such. You see, there's an alternative there: rather than use the FSS to shoot all the blue blobs, you can just drop at the system's nav beacon, scan it, and you get all the signals revealed too. It's quite telling that pretty much all of the guides recommend doing this in lieu of using the FSS, with only some even mentioning that the FSS is an alternative, despite the FSS being faster at this task. But I think you can tell how fun people find it, and how fun internal testing must have found it for bubble players, seeing that all the discovered bodies are revealed there.
So yeah, in my opinion, it's quite telling how there are viable alternatives to using the FSS, as long as you don't go exploring. (Or if you're exploring for NSPs, because not using the FSS for those is actually superior.)
Oh, you could also try asking folks why they explore, which is more important to them: because they enjoy the gameplay of the FSS, or because they enjoy the galaxy? Which is more important to them? There's some food for thought there.
I'd say though that the problem goes deeper than Frontier hastily slapping together a mini-game (sorry,
@Ozric , but you know that the audio team could put in considerably more work than the person(s) making the rest of the FSS), there's a problem of gameplay mechanics. Specifically, I'd say that the primary gameplay loop of exploration shouldn't be body scanning. Rather, it should be actively looking for phenomena, analyzing and interpreting various signals, patterns and the like, flying / driving / walking around to search for and find what you're looking for. (In this regard, the DSS was two steps forward, one step back with pinpointing the precise location of POIs: you don't need to search for them. Pewpew the planet, and there you go, you can drop in right above what you're looking for.)
But well, this is a legacy of the game's launch: exploration couldn't have had any other gameplay then, because we didn't have any landable planets, and practically zero content out in the deep galaxy. Pretty much because the launch schedule was tight, exploration was not a priority, and it's not like there was a lot of content inside the bubble as well.
Of course, that was then, and here we are now, six years later. Horizons was a good step forward in respect to this, especially considering how the SRV waveform scanner was much better integrated than either the ADS or the later FSS, but Beyond Chapter Four was... well, let's just say a mixed bag. Some good ideas, let down immensely by hasty execution and some poor decisions. (I'm not talking about just the FSS here, but also the NSPs, the Codex, the DSS - everything that came with the update.)
So hey, it has been two years and counting since exploration received a major update. Before that, the previous such update (Horizons 2.0) was three years earlier. We'll see how Odyssey will be like (and when): hopefully, by this time around, they'll have gathered more feedback earlier, designed things better. Hopefully, we'll spend less time with body scanning (which pretty much means only the FSS at this point) and more time exploring more actively.
But for body scanning, I think the best would be to get a better integrated means of doing it (not a clunky out-of-cockpit mini-game bolted on top), then having the game alert you to potentially interesting stuff. Functionality similar to
Elite Observatory could be built in (rare orbital configurations, planetary characteristics etc), and if you wanted to find various phenomena, sites or such that were there, then you'd have to fly and explore actively. A more engaging process, for more engaging rewards.
Even the DSS could be much better if it told you what it found, but not precisely where it is. For example, "Biological Signal 32: Bark Mounds", and using the current "search zone" mechanic. Rather than the current unnamed signals and a precise location.
In any case, in a few months we should see how important Frontier thought exploration for Odyssey.