Class for a bad player

Alright, real talk. I’m an older gamer (44) that has loved 40K since 13 and my reflexes just aren’t what they used to be. I’m terrible at dodging and parrying. So far I’ve put most of my time into heavy with multi melta but unless I match with some really good players I struggle beyond the second difficulty. Is there a class/build that is more forgiving to a bad player or do I just need to come to terms with not being able to do higher difficulty operations?

PS please go easy on me here…I recognize my skill level lol!