7 little things that make Melee hard and you maybe didn't yet know about

Most of these boil down to this: Either you aim to be frame perfect and risk a missed input or you take it slow and have no such risk. Many of these stem from the game not buffering most of your inputs. I believe that these are essential to Melee's character and they should never be "fixed". Aiming for perfection often comes at a risk of screwing up big time in this game, and that's just how it is. That's cliff wait, crouch out of run and jump cancel issues

Port priority is a real issue, which comes from a game design choice of updating character states one by one instead of simultaneously. You can't fix it without fundamentally changing how the game works. The best we can do for a potential fix is always have the player who is behind have priority

The shield transition issue can be fixed by disabling light shield on one of your triggers. Then you light shield with one and emergency shield or power shield with the other. You can't L-cancel with the disabled light shield one without locking you out of some tech windows

The wavedash OOS issue rewards players willing to learn to shield and wavedash with different shoulder buttons, so it seems fine

Finally, the dropped input frame every now and then is just a straight up oversight and should be fixed