Well Boros in GRN is an out-and-out aggro deck. I'm not sure what RW is in Dominaria. You could of course just draft goodstuff, but some of the RW cards are quite aggressive (Tiana wants auras/equipment for example, and so does Valduk / Champion of the Flame). At that point, Fiery Intervention and Seal Away aren't at their best. At least, that's how I think of it. Fight with Fire is obviously superior to Fiery Intervention, but it's also powerful enough that I'd pick it over any common so it doesn't count.

I'd splash Fiery Intervention if given the chance, valuing it about as much as Cloudreader Sphinx usually.

About Windgrace Acolyte, I wouldn't think about it that way. Just pretend that all those cards were at the bottom of your deck and were therefore never drawn. The mill effect is on balance good - it enables things like Squee and Whisper, Blood Liturgist.

Re: Gwent - there's a lot that can be said about Gwent, and it's more complex than "play higher numbers". There're things like engine cards that create points over time, there's swarm strategies, anti-swarm cards, the fact that some cards are clearly more powerful than others (gold > silver > bronze), deck thinning as a consistency tool, and so on. Three rounds is also a big deal since deciding when to pass is not easy. You have to try it yourself (or see the Magic Duels subforum). As I'd guessed though, I'm not currently playing Gwent because I can't be bothered learning a completely new meta

Always seems to work better for your opponents anyway.

DOM is so skill-intensive.. normally after a loss I think "Well, nothing you could've done". In DOM there are so many different possibilities, I think the kicker mechanic is an integral part of that. Cast it now to be on curve and to gain tempo or hold it back until later? Equip my weapon or play a card? Clutch his 4-drop now or wait for a bomb?

I just draft bad decks.

Like for ezample I kill opponent's tempest djinn and he casts a 2nd one next turn

[...] the Mythic Uncommons The Eldest Reborn, Tatyova, Benthic Druid or In Bolas's Clutches.

The Eldest Reborn is a tad weaker than Clutches and Tatyova. In fact, IMO the four mythic Uncommons in the set are In Bolas' Clutches, Icy Manipulator, Fight with Fire and Tatyova (in roughly that order). I would still take Eldest Reborn over any Common, but there are quite some cards between Tatyova/Fight and Eldest IMO.

The Eldest Reborn is a tad weaker than Clutches and Tatyova. In fact, IMO the four mythic Uncommons in the set are In Bolas' Clutches, Icy Manipulator, Fight with Fire and Tatyova (in roughly that order). I would still take Eldest Reborn over any Common, but there are quite some cards between Tatyova/Fight and Eldest IMO.

Personally I'd take Icy over almost any card in the set. Pick one I'd take Teferi, Lyra and Aryel over it since they can be so game winning. Pack 2 I'd take Icy over them unless I was already in at least one of the right colours. Icy is such a strong card, if a little bit slow ( if I was only really in one colour and open I'd have to think pretty hard). A lot of the other strong mythics are slow and reasonably easy to answer - Multani would give me pause if I was in green, think that'd be a close one.

I think you overrate The Eldest Reborn a bit. Don't get me wrong, it's a great card and a high pick, but it's not that good. The problem is if you play it early you might not have a good card to bring back with the third chapter; if you play it late, the opponent might have lots of small creatures already and the first chapter is not effective (besides opponent might be hellbent and the second chapter isn't effective either). I think Modulo is right about where The Eldest Reborn is relative to the real mythic uncommons.