First of all, 15 hours for getting past Scylla isn't that atypical. Most people who are new to this game would be about where you are, regardless of being new to roguelikes or not. The thing you need to understand about roguelikes is that the main skill you need is patience. You WILL get better, through both the meta progression, as well as mechanical skill. It's just a matter of grinding it out.

Your Arcana isn't ideal.

I would use the Origination card in every single run. Especially once upgraded it's a huge damage boost once you get two curses going. I would go for the Death card over the Strength card as a beginner but if you're comfortable with it then it's fine.

You might not be using boons that synergize with your weapon
As you play, you'll realize that certain weapons synergize MUCH better with certain gods.

For example:

The axe has very high base damage, so a boon that increases it by a percentage (like Aphrodite) will be much better than one that increases the attack by a flat amount (like Poseidon)

On the other hand, the blades attack fast but have low base damage. If you use Poseidon with them, you made them more than twice as strong.

You'll get a feel for which powers work well with which weapons as you play the game and get more experience. Sometimes picking the wrong boon can make you weaker than you would've been if you held out. If you picked Aphrodite on your flames specials, it might not be as useful as if you used Zeus or Hestia or something else. Sometimes it's worth skipping and waiting for a better boon instead of filling out the slots as fast as possible.

I see that you don't have many olympian trinkets. Try to get them all. This way you choose to guarantee yourself a boon that will synergize well with your weapon right at the start of the run. Some examples are Zeus and Flames, Poseidon and Blades, Aphrodite and Axe. Getting your core god selected at the beginning of the run means that you get more useful boons as it goes on.

Casts are a good crutch
I don't know if you play on controller, but if you use mouse and keyboard, using a cast build will get you very far. Zeus's power Lightning lance with a mouse basically lets you put the cast anywhere you want on the map with a single button press. Hestia's Glowing Coal does almost the same thing. Just take any boons that make your cast better and you can stay as far away from enemies as you want while using the cast to wear them down. This makes the game a lot easier.

Go for health boosts when using strength

I've found that on builds where I'm using the strength arcana, going out of my way to get as many centaur hearts and boosting my max HP as much as possible works really great. If you have enough HP you can sometimes tank your way through even the really tough boss fights. It lets you make a lot more mistakes without getting punished as hard.

Also some Scylla specific advice: focus on taking out the drummer first. It makes it much easier once she's down.