You make 2 mistakes here.
One is comparing Alexander savage and Coil savage. Mostly because there was nothing to do in coil savage once you had beaten it (it was a skill check, for bragging rights), while Alexander savage is our only difficult encounter in the entire game (If we are to consider Ex primals as mid-core, that would make 2 with Thordan I guess). Regular Coil difficulty is nowhere to be seen as of 3.0 onwards. Alexander Savage IS the spiritual successor of regular Coil, no matter how people might try to twist it. And it failed grossly at that.
The second is thinking that people wanted story + harder.
I was of the people asking for a story version. The idea was to have a nerfed + echo version, in order to leave the regular version of the raid untouched, and released after the regular version. Most of the people complaining of Coil ease weren't even ding Coil in the first place and were barking about the 1 week clear of Lucrezia.
Now Alexander story did the difficulty quite right (imo a bit too braindead but that's ok, it's story mode), but the release timing was horrible. You chunk off a lot of incentives of doing savage by releasing the sory mode before even entering the difficult mode, especially considering the abusive dps checks of AS3 (or even Faust-sensei at release. Many groups were crying back then, spending a few weeks on AS1 trash only) which only discouraged the players and further reduced the raiding scene.
Nevermind the release timer. Onto Alexander savage's difficulty then. Most if not all serious raiders at the time said it. It was bad design, purely revolving around dps checks. To the point they abused a game flaw to get an easier enrage timer on AS4 (I know the strat is valid because devs ackowledged they failed to see the issue beforehand and never fixed it, blah blah blah). And when people massively asked why the heck we only had an idioticly hard "deeps onry" version and not a coil-like difficulty, the answer was "not enough staff to do 3 tiers".
Now I get it, they don't have enough people and all, that's fine. No 3-tiered raid difficulty. That's fine. But then, you have to look at numbers to check if it's worth to have this tier or this other one. And if we look at (unofficial) numbers, we have a pretty high rate of Story mode clear (official numbers as of August were 200k clears or so iirc) and an awfully low clear rate in savage : 0.075%. Looking back at Coil after 5 months, 15% clear or so. It's braindead to know which version is the best use of your time to develop if you don't want it to be trashed away day one.
Alexander savage was a mistake imo, speaking from a "development time use" point of view. Especially because it created a desert in mid-core content, leaving people with nothing to do. Errors happen, that's natural. But things need to change if we want a healthier mid-core scene, because continuing down the "braindead story + absurd savage" road will only hurt the raiding scene further.
2-3 days a week is not really casual raiding. More like normal raiding scene (midcore), while your 4-5 days is pretty much hardcore raiding.
The "casual" raiders I know are going out once a week, on week ends, because they can't play for hours straight during working days, if at all.
To each their own I guess, but casual is really misused nowadays.