Fear is not a shield. The slash is the dash.
On a more serious tone, I don't think dashing being added would be a good thing. My reasons are as follows:
1 A dash function would be redundant with the slash one.
2 Dashing doesn't really fit the game's aesthetic. If I understood the little lore we have well, then these memento mori are paragons of justice delivering death to all those who they think deserve it. Dashing and jumping out of the way doesn't really fit such a character.
3 This is a bullet hell. Classic, genre-true bullet hells DO NOT have dashing.
My advice: get used to slashing. It's easier said than done, it takes a while, but the reward is worth the effort. Maybe. I think. I guess? I don't know, I'm still stuck on the third phase, trying to find a better way to play that one. But this demo looks awesome, so its ending must be just as awesome and is surely worth it. So yes, that's that.