I think the problem with Roman Reigns is he still lacks a character.
When kids were growing up in the 1980’s you could ask a young wrestling fan to do an impression of Hulk Hogan, Randy Savage, The Ultimate Warrior, “Rowdy” Roddy Piper, etc. and they would know who each guy was. When kids were growing up in the Attitude Era they could similarly do impressions of The Rock, “Stone Cold” Steve Austin, The Undertaker or DX. Ten Years ago kids could do impressions of John Cena on a playground, easily. I can’t imagine what kids doing an impression of Roman Reigns would even come up if you were to ask them.
WWE seems to have mistaken a spear and & a punch as a persona. Until Roman Reigns has a defined character and personality fans will never see him as “The Big Dog” they’ll just see him as “The guy who still dresses like he did when he was in The Shield”.