Okay so, I'm actually on my phone rn hence the weird ss lol.
If you look at the current starbucks website, they used certain imagery, colors, and typography. As a user when I look at it, the "design" "feels" fresh, refreshing & joyful to me and that is their (the brand's) message. That is what they want their cutomers to feel about their products. That is their direction. And since I've connected to the brand, I feel tempted to try their products atleast once.
There you have it. I tried my best to explain what "Depth/purpose in designs" mean. And that's what I think your design is lacking.
when it comes to web designing, brand guidelines plays a major role actually and no you don't always have to build a brand first in order to design a website, you can just ask chatgpt to write a brand guideline for you.
Or another simpler way would be that you can just try writing down how you'd want the viewers of your design to "feel" when they look at it e.g, happy? Confused? Sad? Joyful? Mindblown? And then you try to design something that resonates with those feelings. You may even use that to look for inspiration like you can go to pinterest and search up "playful websites" "mindblowing websites" etc.
Designs with purpose and direction always turn out to be more impactful and great.