if he didn't have it he'd be way stronger now. he got sharingan and that made everything easier and he focused on being able to properly use his chakra exhausting sharingan and raikiri. before he was already learning earth style, lightning and who knows what else. if he hadn't been given some free power up (which is how kishi loves to ruin characters) he would have sought out training from minato to learn new jutsu and maybe even hiruzen. he also would have had way more taijutsu training with gai like when they were kids and he didn't have sharingan which would have put him slightly below guy in taijutsu. but sense he got the sharingan he hasn't been shown training with gai in actual fights just stupid competitions because having a sharingan put gai at a disadvantage and kakashi probably didn't feel like shaming him when they were younger.