I don't "get" arena

~1350 ELO noob here. I've been playing semi-seriously for a few months and I feel like a have a strong grasp of the basics. I feel pretty comfortable on all the land maps that have been in the RM 1v1 pool since I started, except for Arena.

I just don't understand it. Obviously since you start stone-walled you're encouraged to go fast castle, which is fine. But from there it feels like a convoluted game of rock-paper-scissors in most civ matchups:

1. Straight booming beats a mix of eco and military, but loses to all-in Castle Age aggression OR fast Imp
2. A mix of eco and military beats all-in Castle Age aggression, but loses to straight booming OR fast Imp
3. Fast Imp beats a mix of eco and military OR straight booming, but loses to all-in Castle age aggression
4. All-in castle age aggression beats fast Imp OR straight booming, but loses to a mix of eco and military

There are some other corner cases of course but these are the broad strokes I've identified. The problem is, you literally can't scout anything your opponent is doing in their base or pressure them at all without a huge investment, so aside from divining obscure details from watching their score, you just have to guess based on the matchup what they might be going for.

An example, but this is in no way the only example you could think about: any civ vs. Turks. The standard play from Turks on Arena is fast Imp into HC/BBC push. This is next to unbeatable if you're just booming, so you have to prepare a sizable military (knights, maybe) shortly after reaching castle age in anticipation of defending, or else attack them in very early castle age before they can get up to Imp. But hey, Turks don't have to go fast Imp. If the Turk player is just playing a standard FC into three TC's, you're way behind if you try to go forward siege or make a significant military in early castle age. And there's no way to tell!

In practice what this means for me is that I'm almost always getting taken by surprise on Arena and winding up getting countered in the above rock-paper-scissors. The only solution to this I can think of is to just play really non-standard cheesy strategies like Incas trush or Slavs Longswords + Siege Tower... but that feels like it's just avoiding the issue rather than addressing it.

Can anyone explain what I'm missing? Thank you!

(Some winrate stats for me courtesy of aoe2.club to illustrate the magnitude of this issue:

Arabia: 55.32% Golden Pit: 59.26% Hideout: 57.14% Arena: 48.84%)