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Erayo, Soratami Ascendant doesn't see play because it's pretty hard to set up.  You'd have to put it in either a Storm or Affinity shell.  In a Storm shell, it would take slots away from what you want to be doing more: making mana and digging through your deck.  Sure, it's protection the turn you go off, but it's mediocre protection because if you can already cast 3 other spells, you're not going to fizzle any way.

In an Affinity shell, it takes slots away from things that kill your opponent.  Plus, it requires you to hold cards in your hand until you play it, in which case you're losing a ton of speed.

It cannot be played in a control shell because a control deck would just rather have higher impact cards in hand than a bunch of cheap effects that will eventually generate an advantage.  The cards in a control deck need to generate advantages immediately, not in a turn or two.

Basically, there doesn't exist a deck in the format where you could reliably set up Erayo.  Even if you could reliably set up Erayo, there doesn't exist a deck that could make use of the advantage.

Braid of Fire is just bad.  What deck would you possibly want to only generate mana on your upkeep?  Most game ending spells are sorceries, at which point you need a third card to make Braid useful.  On top of that, you only generate a little mana at first.  That means you have to survive for a really, really long time for it to be truely useful.  On top of that, Braid is just a terrible card.  You trade a full card for what?  Maybe 3 mana total, in a phase where you're "down" a card and constricted on what you can use that mana for.

I think you really need to brush up on how to evaluate cards for playability.  For example, a control deck would never want a card that just produces mana.  The decks already run a ton of lands (usually 25-27), so they never have problems getting mana.  They need to run answers or ways to find those answers.  Saying Braids would be good for control is insane because it costs you a card, but doesn't answer anything.  Saying Erayo is good in aggro is similarly insane because aggro doesn't card about the number of spells cast or restricting your opponent's choices.  They just want cards that kill the opponent.  Saying Erayo is good in control is similarly bad because they don't want to spend all their major resource (cards) at one time, only to lose when the opponent goes Deceiver Exarch in response to the flip, untap, Gitaxian Probe (for free, gets countered), slam Splinter Twin on Exarch and then kills you because you tapped out to dump your hand to Erayo.

Compare what you want to do with Erayo to what most other decks are doing on turn 4.  You want to strip a card and draw two cards.  Storm is going to be winning the game on that turn.  ExarchTwin is going to win the game (after an end step Exarch).  Jund is going to cast a Bloodbraid Elf and pull extremely far ahead.  Affinity will be kililng the opponent in the worst possible case.  It's simply not powerful enough to just set up a grindy advantage card.

Braid still doesn't do anything, even it made mana of any color.  The instants just aren't that powerful, and your upkeep isn't when you want to be casting instants any way.

I understand perfectly why control runs as many lands as it does.  It needs to make all of the land drops because it needs to have the ability to start providing answers and a threat in the same time.  It also needs to hold it's answer cards in hand until it's time to use them.  If it misses land drops, then it has to start discarding earlier, which means getting rid of answers.

The problem with thinking of Braid as a signet (which do see some play) is that it doesn't make mana the turn it comes down.  It also doesn't make mana whenever you need it.  The format isn't too fast for 2-mana accelerants.  U/W Control, U/B Control and some Tezzeret builds run signets (and talisman ).  However, they're not really for acceleration, it's for playing around Blood Moon .