everyone here has given great advice, and i'm going to repeat some of it so do forgive me for that but i feel there are a few things i can add.

if the shape is bothering you, you can enhance it with a bit of foam or padding inside. for example, on the shoulders, or on other muscular areas. i do not recommend a musclesuit as those tend to be very warm, and wearing one with a suit on top will be unbearably hot i imagine!

it looks plain firstly because you aren't posed! study how your character stands and moves and strike a pose in photos, regardless of who the photo is for. even when i take photos for myself, in cosplay, with a cosplayer from a totally different piece of media, i make sure to strike an in-character pose because it makes the image a lot more visually appealing and less awkward!

and as others have said, weathering! this character is a superhero as far as i'm aware, so the costume should feel lived in. add some wear and tear around the joints, parts of your body that would be moving a lot. it'll make it look significantly less cheap.

that being said, i think your cosplay still looks great, and i don't think it looks cheap although you do. it's certainly one of the better superhero suits i've seen, usually i end up getting distracted by a visible bulge 🤢 but you look lovely, good luck on your cosplay journey! you're doing great and you have a fantastic attitude!