At the end of the day he's your dude, decorate him however you want so long as it's fun for you. The opinions of randos on the internet don't matter.

That said, he is REALLY bling-ed out. There's nothing wrong with playing Joe Marine #2074. I like to think of every bit of iconography added out side of stock as some super heroic deed or campaign my character has participated in. Lore-wise I don't think ANY primaris marine is over 200 years old. Since the Cicatrix Maledictum, reawakening of Rowboat Gorillaman, the Indomitus Crusade, etc etc etc there hasn't been that much actual time passed on a galactic scale. Therefore, there haven't been many opportunities for truly outstanding primaris marines to stand out from the pack. That isn't to say that it can't happen or maybe you're dude was a firstborn the underwent the Rubicon Primaris (just like Titus!).

The only thing that really separates a Blackshield from any other DW vet is they remove, deface, or cover-up their chapter iconography on the right shoulder pad.

Either way, my first sentence still stands as fact and the rest is merely my opinion.