The primary game mechanic of Vagrant Story is switching weapons to suit the foe you are fighting, and correspondingly that said weapons evolve to better suit those situations. The notion that you need to deliberately grind for this to happen is simply not correct, unless you consider not running away from every enemy you meet to be grinding, in which case I am happy to agree to disagree, much the same way that I don't think that
Fallout 1 is a ten-minute game. Just the equipment you find in the normal game, without any drops at all, allow for plenty of interesting crafting options, and just a few random drops allow for a lot more options. Similarly, the normal growth you get in the game just by fighting enemies with the right weapons while you're exploring is perfectly sufficient to make a very substantial difference in how effective your weapons and, by extension, you are, by which I mean is that your weapons actually do damage instead of dinking 1 HP with each attack against this or that boss.
I should point out that you
can indeed grind in Vagrant Story to build things like Damascus Holy Win blades with 100 in all stats. This is broadly equivalent to, say, grinding Deathclaws in Fallout to get to level 21 and get the highest-level perks, that is to say, entirely unnecessary for any normal playthrough. The fact that you don't consider getting Slayer to be worth the effort spent in Fallout (as, indeed, it is not) does not mean that developing your character was entirely pointless. I think it's entirely fair to criticise Vagrant Story's crafting system for being needlessly opaque and complex, but to say that it requires grinding is a misunderstanding.