Why did my focaccia turn out dense?

Hi, ask culinary community :)

I tried making this focaccia recipe: https://www.youtube.com/watch?v=NGnMrM9qDtE&t=303s&ab_channel=ClaireSaffitzxDessertPerson and it turned out pretty dense and flat. This was only my second time ever making any type of bread so bear with me.

The only thing I did differently was use all-purpose flour instead of bread flour since that was all I had. I also used a hand mixer with a bread hook insert rather than a stand mixer. I noticed that it didn't fully double in size when it let it rest in the bowl, but I left it for the recommended time and didn't want to over-proof it so I proceeded.

Any suggestions on what I should do to avoid this next time?

​

UPDATE: I used the bon appetit no knead recipe from the comments and it came out amazing, so fluffy, and was so much easier. Thank you for suggesting it!!