Celerity should be added as a passive effect to Phase Rush and be removed as a rune entirely
Considering 4.5% movespeed quints were only niche on like 2 champions who both happened to be Stormraider's Surge users there is no reason to give so much passive movespeed to so many champions that are already hyper mobile or mobile and don't even need it. It's already frustrating enough to play more immobile champions in a game with too much mobility but to give those same hyper mobile champs a bunch of passive movespeed on top of it is just too much.
It took 3 quints to get 4.5% movespeed for a reason Riot....... and there is a better rune you could create to replace celerity on top of it.