Neither of them is difficult or challenging. But the ADS was "hold button for 3 seconds, success".
The new equivalent of fully scanning a system now is called mapping it. Look at the use cases:
Actually, I think that's pretty subjective. It depends what you're looking for. Of course if you are looking for POI's then mapping is the thing, but mapping for the sake of it - not so sure.
And after explaining this, i can go back to the "challenge" thing. It's a bit out of context the way you see it there. We have some users here who in many threads were all like "but now it's impossible to find such stellar oddities". Where in fact it's just as well possible, but now you have to do a bit of gameplay for it.
For me it feels a bit like they are looking for diamonds. But only if they can have a magical diamond-finding-rod. Without magic to give them diamonds, they don't care for them any more. And that's why i sometimes point out the "oh how challenging the old ADS was". A number of postings here are all about eliminating newly introduced gameplay.
Again, this is the view that having seen what's in a system it is then explored, which is obviously not the case. Both the FSS and the ADS have equivalent gameplay up to the honk. The difference being that the FSS actually scans a bunch of stuff, like it or not which the ADS never did.
Nobody is arguing that the FSS doesn't add active gameplay, I acknowledge that in plenty of posts. And I also don't think anybody is asking for the FSS to be changed or removed, just have the ADS reinstated as an alternative way to get a system overview. The issue however of having to do gameplay for the sake of it, not because there's a specific goal or reward at the end is IMO poor game design.
The FSS doesn't expect players to have to scan a whole system just in case there's an ELW in it. A player will know as soon as they glance at the spectrum if an ELW is present without having scanned anything. Likewise if players are looking for POI's, they don't have to fly to the planet and map it in the hope that something might be there, they will know that for certain by scanning with the FSS before they decide if it's worth engaging in the gameplay of flying to the planet and mapping it.
Why is it so unreasonable that players looking for oddities shouldn't have the same experience. To be able to know something interesting is there so engaging in the gameplay has a purpose. To expect players to scan every system in the hope that it contains something interesting (and that something is far more rare than ELW's!) is bizarre and surely not good game design.
I mean, if you want to use combat as an example, that's like FD saying an assassination mission target is out there somewhere in a system (and specifying one system is making it far too easy, but we'll go with it), however we're not going to tell you anything about it, you'll just have to destroy every NPC you come across in the hope that it's the right one - it may take some time. You know what, I reckon there'd be some complaints...