Is it too late for me to improve it?

Hey guys im 21yo baller , always had a problem with my vertical i play basket since 15 have super decent handles and shooting..played with pros too , but i never have been able to get any inches on my vertical my vert is 18 inches and i cant even touch backboard as im 5'7 lol...is it too late to improve it now? i also readed VJB 2.0 and some confusions were that he mentioned Mike Rippetoe saying that vert cant be improved more than 30% and also vjb author says that not EVERYONE is capable of putting 15 or more inches on their vertical jump...I also dont have experience with weightroom.. Can anyone help me out give me some ideas is it possible or i am just wasting my time on something thats purely genetic? is it possible for me to reach 30 inches vert in like 1 year of training?