Using zerglings effectively
Hi, I'm a casual ladder player in Gold League and I wanted to know how to utilize zerglings effectively against non-zerg opponents. For context - I've been watching casts of high level zerg players and I noticed that often they are prioritizing upgrading melee attack over ranged in many of their games. Of course this means that they plan on using ling-bane compositions to deal with their opponents. I tried replicating that style in my games, but I've found out that just using hydra+roach based compositions seems to be much more effective. The problem I have with lings is that opponents tend to wall off and I can't seem to get value out of them. Apart from that I feel like most of the games are decided by 'all-army-hotkey' attack that will lead one player to their demise. There's barely any harassment from my opponents so lings can't even be used defensively. The only way where I find them useful is when defending from 4 hellion opener. I want to add that I'm rather a macro focused player, so in most of my games I try to go for quick 3-4 bases as I'm not punished that often for that. I know that I can use them to limit the ability to expand, but rarely I manage to find something in the open which isn't immidietely walled off by 12 cannons or a planetary. So my questions essentially are - is my understanding of zerglings' role correct? Can I really use them on my level in the same way as pro players do or is this style caused by more frequent harassment?
EDIT1: One more question - why players so often start with +1 melee as first upgrade even if their comp is 90% ranged?