Msot memories over bronze rarity are just gimmick but somes are very good on very specific teams. Crit Act memories helpsa lot on Crit teams. The 15% React memory is very good too and saved me several times.
I don't know how it will turn in the future but right now, memories as they are are not necessary to beat the game. I'm not a big fan of it but I take them as a little bonus I got here and there with Memory seeds more than a must have mechanics like Ampies/Centies or equipements.
If I got a good one, I use than good one, if not, I use the regular bronze memory.
Before that, Turn 1 ATK and Weakness DMG were the default abilities when nothing was more usefull like provoke/HP up. Now, there is just more default choices when a girl don't need a necessary ability to show her best potential.