As someone who's done FFFF2 twice without Yendor by now, I can assure it's not critical, but it DOES bypass the single hardest part of the run, and that is lvl1-3. Simply getting a run off the ground is the hardest part of Phantom Citadel. If you can manage it via boons/good shop items,then making it to lvl 6 or so with a dragon shield/head start on your JJ/Dracul/Pactmaker boons means you're in great shape. If you score Apheelsik as well, you may have well won the run.
That said, prepping More Glyphs for apheelsik isn't worth it IMO. You really want attack boosters in this map, because Phantom Citadel emphasizes regen fighting and every advantage you can get in said regen fight is going to be a massive help, which is also why prepping dragon shield and getting out of the early game hell makes such a massive difference in its own right. You can get away without apheelsik just fine, but you can't really make up for having -20% damage against 2 bosses with weakening strike, 1 with frostbite, 1 with corrosion, and 1 with curses. You really want your damage.