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Complex abilities CAN have a place. But GF does them wrong. Simple abilities ARE nicer though. LoL back when I played is a good example. Early(passives) abilities were just "8% Lifesteal" or "Gain 8% MS" or "Gain bonus crit"
Then we got "Allies move faster towards you" . "Turn invisible if you stand still" and "gain a shield periodically " problems started after each ability did many different things. "Gain double crit that deals reduced damage and a shield by moving" or "after damaging an enemy get bonus MS, walk out of range do get more range and MS and bonus damage."
THEN we started getting textbooks. Actual 5 paragraph abilities. But, while most of the time this was awful. Sometimes it was good. Jhin is the best example. Ability is long and complex, BUT makes him fun and unique. And part of this is because they made it have weaknesses to balance out. Gist of it is, "you shoot slower than everyone else and can't boost this. But every 4th shot nukes them." Also a reload mechanic and more, but it makes him unique AND fun, but isn't overbearing or feel overloaded since it gives him a drawback to having it. Something to play around that is also fun to accomplish.
Pokekon abilities being complex can be fine IF it is done sparingly and to make something thematic and fun. Wishiwashi is best example I got so far.