Shouto knows his suit design is ugly, and he knew that it’d piss of Endeavor.
Not that he really had any ideas for a better one, never being able to use his imagination as a kid crushed a lot of his creativity, but something so plain would’ve never been approved by the flaming bastard so he went with it.

It doesn’t give him any advantages with his quirk either,

A few years in of being a Pro Hero and lots of people questioned the design, many said it was ugly or that he’d be mistaken for a janitor.

After seeing a few magazines, a picture of him and Izuku fighting two villains in the city, hearing a comment about his suit being kind of hideous, he glances to the photo again, and gets an idea.

The next villain attack he shows up at is just after he picks up his new suit, seeing live footage on the screen he rushes to where the confrontation is taking place, police already on scene and trying to stop the woman shooting spikes at civilians,
His outfit only slightly flashier now, temperature gages to know when to regulate but mostly just white and blue design, a few bystanders notice his suit as he defeats the attacker.

Soon gasps are heard from press that crowded the scene, Hero Shouto is trending and halfway across the city Izuku drops his bag of fresh muffins as his face tries to light on fire.

Across the back of Shouto’s suit is a large heart encasing the image of a very familiar green mask with bunny like ears.

Shouto says nothing to the flock of reporters hounding him for answers, he believes it’s fairly obvious.
He smirks walking away, thinking of hour furious his old man would be right now, before pushing the thought away. He had a date to get to, a date with the #1 hero Deku.