Transitions easy ease controls and custom curves
All transitions lack the ability to customize therefore kill their usability to a custom preset for ex to make the simple fade you have to apply twice th effect with the keyframed opacity control - on both the previous and the following clips in order to have that custom look. but it is better to be able to sutomize the transition effect with cross dissolve so you could roll trim without having all keyframes to be offsetted.
effects that are so common that lack of customizable easing are:
Dip To Black
push - also there is no option to further the distance between the clips - sometime it is exactly needed to have them separated with an empty space and again you have to do it with transform effects instead