It's pretty simple but SE is incapable of making it and they have to accept that at first the game won't be a mega blockbuster.

1) Bring back menu based combat but make it more interesting than just spamming Attack.

2) Drop the cringe Asian writing/humor and nu-anime tropes. Older FFs took themselves seriously 90% of the time and jokes were sparing enough to not feel obnoxious.

3) Simplify the design of everything. Post FFX characters are forgettable because they are over designed fanfic looking characters. And while they're simplifying character designs, simplify the graphics too. The more realistic vidya graphics get the less memorable and inviting they look. FF7 Remake is a prime example, where you have someone straight out of an anime walking around generic looking normies in normal looking locations for most the game. Lower the graphics down and stylize the fuck out of everything. And let characters be sexy again, Tifa wouldn't be half as popular if her remake burkha had been the original design.

4) Find someone who can make incredible memorable orchestral music and let them cook.