I totally agree, it's tough to subtract from this. I feel as though Ayara is actually the weakest card in the list, one of which is secretly supposed to be Midnight Reaper #4 but also gets support from Erebos.
I thought quite a bit about Mayhem Devil. The level of aggression it would provide seems really solid between Oven, Ayara, Plaguecrafter, and the Titan offing itself occasionally. I don't think the deck wants to be that aggressive though. Aggressively drain my opponent's resources, yes. I don't think I can support the actual desire to run across the table into my opponent until a bit later than the Devil may want. Additionally, it seems to really crowd the 3 drop spot and the deck is quite focused on getting all three different CMCs to set up powerful Menageries.
Bonecrusher is essentially just for
Apostle of Purifying Light, I don't actually like Bonecrusher in the list at all, but 10 sources might be a bit low just for getting Kroxa on T2 which feels important. Burglar Rat was much easier to hit, lol.
I don't actually think I need to try to fill my yard. If they aren't hurting me, I am going to slowly eat their resources with my various means of discard and sacrifice. If they aren't even casting creatures... I'm attacking and winning. If they are casting creatures, then I can afford to block and play my game of absorbing them. My mastermind play that might have been missed is actually sacing Kroxa to Plaguecrafter on the Menagerie since I can stack the triggers. Kroxa feels very flexible and abusable in this list.
Glowspore was in the deck waaaay back before even War of the Spark was out and I wasn't into Standard, I was just making set restricted 40 card guild decks (I had all 10 at one point). Needless to say, you're probably very correct that Jund is not a mana base I want to rock. Actually the list I was playing Saturday was BG because I had no need for Red. I was using literally just Cavalier of Thorns to get extra Menagerie. The self mill was nice, but it was also unnecessary; Oven and Crafter make that easy work.
When I was writing this up for THB, I wanted a devotion sub theme. That's actually how Ayara got in the deck, Erebos was going to be there no matter what, lol. Gary just didn't make the cut. The sideboard is very loose however; what I said about Bonecrusher is the case for most of my sideboard cards. Enchantment removal, artifact removal, (pro-black) creature removal. I'm sure I'll not need that much, but it's all just thoughts.
Nightmare Shepard got a glance not just for Gary, but also for basically everything in the deck. Extra copies of Kroxa become
BR Mind Rots with potential damage. That's really good. I just think I could only support one of them in an Ayara slot. It also feels like overkill. They either have cards and are likely to remove him or they have nothing and the ability does very little for me.
What I do want for the list are things that deal with Questing Beast better and an aggressive 1 drop. Foulmire Knight feels like low man on the totem pole despite still being a good card.
Edit: I'm looking at
Anax, Hardened in the Forge as a mass creator, maybe drop an Ayara. He won't have huge power, but he's got reasonable chance of generating an overwhelming number of 1/1s. It also distinctiveness sweepers on the front end before grave hate can take hold. Then I can still throw 1/1s forward or sac them to the Oven to get food or cats.
I'm also looking at
Careless Celebrant as a bad red card that kills specific things. All I need to do it get it killed and that seems easy.
Lastly,
Irreverent Revelers might be okay as artifact removal? This is again crowding the 3 drop slot, it's also pretty weak. It's competing with Bedevil out of the board, tbh, and in that vein... It's something that can be resused with Menagerie and possibly Cavalier of Night.