But, if they balance it where the parts or items needed are in 'easy' regions, then it's just a matter of exploring and farming for them. and thus progress. Maybe certain things can be 'bought' from traders with credits. So if you can't find it. You can "grind" for credits to buy it for some "price". This is another way to allow progression. Sort of like a pity counter.
Hmm, I actually see those things as the opposite of progression, honestly.
This is just my personal view, but I often see the need for farming/grinding to be a game design failure. I know it's incredibly popular (especially in certain genres that need to extend game time to keep their audience, like MMO's, mobile games, etc), but it seems more like doing chores to me, than it does playing a game/having fun (unless the chore itself can be made incredibly fun). And I think it often discourages experimentation and encourages safe (often boring) play styles and usually requires games to lower the difficultly/challenge at various points, depending on how it's used, to prevent people simply giving up if they're defeated/get stuck.
Just as an example, I'm playing Wildstar with my partner at the moment and there's a Runecrafting system, the concept of which seems really cool. However, the drops are fairly rare and it's very time consuming to farm the materials for it. There seems to be an element of chance to the crafting itself, with little guidance on outcome/how to do it in the first place and once used, you can't recycle the runes back into materials for later levels. And we're still managing to fight through the monsters. So, when I tried to look it up, the suggestion from other players was the same conclusion I'd come to on my own; that it's not actually needed until max level and you should just keep everything that drops until then, so you don't waste it/can convert the materials to high tier runes, and roll the dice then instead.
Basically, the way it's designed discourages players from using a system that could be interesting and cool. It punishes experimentation or early use. And the monsters have lowered difficulty, so you can still survive/win, but combat feels more stagnant and generally takes longer as you slowly wittle down enemy HP.
There's a lot of easy traps to fall into, for crafting systems. Other times, like in World of Warcraft, by the time you could naturally craft something, it would be useless/you'd be many levels above it. Or, in other games like Diablo 3 (especially gems), the difference as you go up the crafted tiers is often so small it doesn't feel any different/like you've made any progress. Imagine if in Dark Souls, there were easy monsters and you had to go back and fight them every time you died to one of the difficult ones.
Basically, I'm just pointing out that you have to consider players time as part of the cost of any crafting system, especially if it might lead to dead ends or require them to redo already played content to get back to the things they actually want to be doing.