Honestly how I would fix material to make it matter in everything is create new types, make a poison material that if its in weapons give players a chance to poison based on tier, add defense like protect,shell etc materia and so on.
For gathers add a materia that adds +1 to gathered items based on tier like tier one gives +1 tier 2 +3 tier 4 +6 etc, for crafters add a probability materia of getting an excellent or good tier and add idk cp regen mats... Like we could make amazing systems with the materia and have fun with consumables.. but
for combat we could add in material that increases exp gained and spirtbinding as well
and for combat ones id make them super rare drops from bosses that way people have a reason to farm dungeons
for consumables/esuna Id A make them a lot more useful and B. make them useable on everything related a esuna should work on all negative effects on the party, same with "golden niddle" antipots etc .. that would fix so many things just doing that alone
id also add a mount in every dungeon that way its another reason to farm'
I would allow people to use this anti fire potions etc in everything same with pots in PVP id allow it this would give so much value to everything in the game, and honestly I believe would make everyone happy. Id also make every fish either useable in a craft/alchmey or id make a npc at fisher guild that will buy them off players for either gil or white scrips.
This would encourage players to prepare and always do their very best that they possibly can in everything and would make so much of the dead content more alive and enjoyable
As for culinary we could get something interactive where we make food for people at the guild, and earn culinary tokens which we can use to get more "rare" things, in fact we could do this with every guild add a repeatable thing with no limits to earn guild tokens/gil that we can spend on w/e