You said interesting/meaningful choices again. Not everyone viewed those interesting choices as fun choices, necessarily, or at least not me. That's the thing, you can recognize the positive characteristics of an ability (variety, flexibility), but that's not where the conversation ends. It's not just, "Well it has positive characteristics, therefore it is a net positive experience for SAM to have it." It should also consider the fun factor, if it makes sense in the core design and goal of the Job, how it feels to use, and how smoothly it fits in with the rest of the rotation. Let's explore some of those scenarios.
I don't find it fun to have 8 seconds left on Higanbana, have the Sen I need to refresh it smoothly, but ALSO have Hagakure coming off cooldown at a similar time. This happens the SECOND time I need to re-apply Bana, so just 2 minutes in. The decision there is un-fun because I have to make a decision of what to neglect. Do I refresh my DoT with the one Sen, which eats significantly into the off-cooldown time of Hagakure, since I have to build 3 Sen again? Do I use Hagakure sub-optimally at 2 Sen, which by the way, also means I'm letting the DoT fall off for multiple ticks? Or do I use Hagakure optimally at 3 Sen, eating into off-cooldown time of Hagakure, AND letting the DoT fall off for even MORE ticks? None of my decisions there are fun. They all have a caveat, or sometimes, multiple.
When Hagakure is still on cooldown (for only about 2-3 more seconds), you're maxed on Sen, and about to complete another combo. Again, you have to choose what to neglect. You have to choose between using Midare, because you don't want to start delaying GCD's to hit Hagakure optimally, or you can what... delay GCD's, or worse, finish the combo without gaining any Sen? Not the choices I want to be making.
Just a couple. Now, that's up to you to decide if you find decisions like those fun. I personally don't. That, and I feel that the Sen/Iaijutsu rotation is the core design of the Job, while Kenki is more like filler. And Hagakure distracts from that core design and rotation. As a DRG I wouldn't want to sacrifice Eyes (LoTD) for more jumps. As a MNK, I wouldn't want to sacrifice GL stacks for more Chakra. As a SMN I wouldn't want to sacrifice Bahamut for more Aetherflow. So on, so forth.
So for me, Hagakure is a net NEGATIVE experience as a SAM, even though I can see it, and respect it, for it's positive traits.