Your hatred of hexproof and your love of Grixis-Heavy-Control-and-Oh-Hey-Heres-a-Combo-Finisher! are connected, you know
I don't think so. I'm not specifically attached to Grixis. It is one of the stronger three-color combinations in Eternal formats, and I've put some focus on Eternal formats over the years. But given the option, I'd take Sultai as my three-color combination. And when possible, I'd prefer to play dedicated combo rather than control with a combo finish. My preferred style of combo deck hasn't gotten much to work with lately and it seems like the competition gets more new tools with every set release. So I'm going back to my control roots somewhat. I mean, there's more to it than just that, and I dabble in all sorts of things. My main format lately has been Canadian Highlander and my decks so far have been aggro goblins, monoblack control (scrapped for now), monobrown ramp/control/goodstuff pile-I-threw-together-haphazardly, and Jeskai Splinter Twin. But overall, I have interest in a diverse array of archetypes. I've become something of an advocate for combo in part because it's among my favorites and in part just because there's an unfair stigma attached to it that I find poisons discourse around the game.
My beef with Hexproof, which I did touch on but perhaps not enough, is that it replaced Shroud. Shroud was a mechanic with inherent balance to it. If I have a Zephid, you can't kill it with Dark Banishing or whatever, but also, I can't enchant it with Rancor. It is, in a very real sense, fair. The fun part, the part that makes the game interesting, is to take that fair thing and work with it, to try to exploit it. Hexproof is the whiney, petulant child version of Shroud, screaming "I wanna be able to target my guy and I don't want you to be able to!" When it came to interactivity, to counterplay, Shroud was far more interesting. And yet WotC caved in and replaced the balanced mechanic with "It's OK, you can have your cake and eat it too."
There are certain individual Hexproof cards that I actually like. Lich's Mastery, for instance. And if WotC had made Hexproof, not as its own Evergreen mechanic or whatever, but just some ultra-special concept to appear on cards where it made sense, then I'd be fine with that. But I think when it comes to discussions of design space and such, they backed themselves into a corner by replacing Shroud with Hexproof. It creates a conundrum. Either the Hexproof creatures have to be weak/overcosted or creature-boosting auras/sorceries/instants have to suck or creature removal spells have to move away from targeted killing. Otherwise, you can just use your good boosts on your good Hexproof creatures and win.
It's not that any particular Hexproof card is even too good in the grand scheme of things. Most of them aren't that powerful and even the few that are really good don't dominate formats or anything. It's that the mechanic unnecessarily constrains design. Like, you mention discard spells. One thing balancing them is that they're sorceries, so you can't use them on anything your opponent just draws and immediately casts. If they made those discard spells instants instead, then it would cause problems because you could hit cards as soon as they were drawn. You might be able to find a way to mitigate that by making them cost more or by enabling opponents to rely more on instants, but it's better to just not go down that road.
Amonkhet is a great set because cycling. Devastation is a great set because Hour of Revelation / Glory / Devastation. Scarab God is a bad card and a bad deck in the tradition of Dimir decks and their entire concept being bad (*disclaimer - I have and continue to argue that counter discard are the elements that make Magic a worse than it needs to be game).
I did enjoy some of the cycling stuff in
Amonkhet but it just wasn't enough to win me over, I guess. I am still messing with some of that stuff, actually. But so far, I'm definitely more enthusiastic about the use of cycling in Onslaught Block than in Amonkhet Block.
You praise Hour of Glory, which can exile cards from your opponent's hand, and then in the next sentence criticize the existence of discard spells? Anyway, I make my assessment of
Hour of Devastation as a lackluster set based on my perception of the quality of the 199-card set, not on a few rare sorceries. And I didn't get into it, but that's a weird call to make, really. I mean, if a set consists mostly of pretty good cards but doesn't have much in the way of awesome build-around stuff, how does that compare to a set with low-quality bulk cards but a handful of great ones? I could see that comparison going either way, but yeah. No set is
all bad cards. No set is all good card either, for that matter. I'd generally rate
Hour of Devastation as a poor set. It did have some good stuff, but not enough to make up for the low level of viability of most of the cards. I was unhappy with the set. It was a disappointment. But I do like Hour of Revelation. That's a cool card.
I probably disagree with you on The Scarab God, but I'm unclear on what sense of "bad" you're using here. Is a "bad card" one that is weak? Popular opinion seems to place it as one of the most powerful cards in the set. Is a "bad card" one that causes problems with rules confusion of design space limitations? I'm not aware of issues with The Scarab God in those areas. Is a "bad card" one that you just don't like? It's fine not to like something but I'm wary of "bad" as a label in that context because general colloquial usage patterns tend to imply that badness is correlated to some objective standard and it is misleading to interlocutors expecting such a thing if a wholly subjective standard is implemented. Perhaps that's too pedantic. I don't know.