Fastest way to gain muscle?

I’ve been hitting the gym almost every day for the last year and a half, completely changed my diet to cut out most added sugars (limiting myself to 22g a day), mostly switched to a protein heavy diet around 120g a day and I am taking in roughly 3000 - 3500 calories a day.

I am 6’6, 220lbs and have literally ALWAYS struggled with gaining muscle. I can get stronger, get cut, but not bulk at all. What am I doing wrong?