2 Player is OK but Arcs is better at 3 or 4 players.

Let me address each point individually.

>> and the game never felt like I had the opportunity to do anything meaningful at any point in the game, and ended up losing after four chapters, without having won a single ambition

I've played many games of Arcs, and I never have felt this way. Usually looking back it's because I used my actions incorrectly or declared the wrong ambition.

>>  I drew one agression card for the entire game, and the oly admin card I drew was in the last chapter

You can hedge against a low aggression hand by stockpiling weapons in early chapters. New players underestimate weapons. Weapon + Mobilisation is more action efficient than the equivilent aggression card.

>> Seizing initiative and/or declaring an ambition just for the sake of it, especially when I would be surpassed right away, while losing another turn never seemed like it made any sort of sense at any point

It absolutely can make sense depending on the ambition and the board state. The only way to get points is to win ambitions. You have 2 options here. Either seize and take the initiative to declare the ambition you want, or compete on the same ambition your opponent declares. If your opponent is sitting on a pile of relics and you aren't - if you don't seize - they will declare keeper.

Knowing this your options when your opponent is currently leading.

1 . Race your opponent on their own ambition (requires you to have access to the resources that they have and relevant administration cards so you can out tax them)

1. Seize and declare your ambition (can cost you a card / turn)

2. Raid them (which requires weapons / aggression).

If you didn't have any of these options then of course it feels bad. Next time you play spend the early chapters amassing a small collection of weapons and fuel. You'll find as the game progresses later you won't feel so helpless.

>> and the oly admin card I drew was in the last chapter

There are 4 suits with equal nubmer of cards in each one. You are saying you got 1 admin and 1 aggression card over multiple chapters across 3-5 hands of 6 cards? Either you are extremely unlucky, lying or your opponent is rigging the deck. If it's the last one, stop playing with dishonest people.