When I started I wanted a sneaky thief/assassin who did not craft or do spells and I used my perks accordingly and the weapons that came my way (notably Chillrend, a fire dealing bow and some good, at the time, daggers). However, by the time I hit the mid-thirties I found that my weapons no longer cut the mustard and I was, despite having 100 sneak, getting into too many melees that my character was not designed to deal with (no armour worth the name). At the same time I was struggling to find, in shops or dungeons, any decent new weapons.
I could kill just about anything if I could get into a backstab position, and, if I could stay hidden, I'd take down anything with my bow, eventually. However, despite what some have posted here, my experience is that it is not always possible to sneak up behind an enemy and it is not always possible to stay hidden. For a start, the Forsworn in particular seem to be equipped with some sort of radar that enables some of them to find me at night when I am unmoving in the deepest of shadows. When you have very low armour and are getting mobbed you need weapons that will take down each enemy very quickly and mine could no longer do that.
I put a couple of perks into alchemy and stole all the decent poisons I could find. Frankly, it didn't do it - the poisons weren't good enough and anyway are one shot weapons. Having a poisoned blade in a fight against five Forsworn or bandits can't help much - the first one might go down, but the four others are still going to be there and I hate the idea of stepping out of the moment to access my inventory in the middle of a fight, feels like cheating to me.
So, better weapons seemed to be the answer and, as I couldn't find or buy any, that meant smithing and, in the longer view, enchantment or, to step right outside role, magic. I am now at level fifty and have Smithing at a 100, which means I have been able to improve all my weapons to at least flawless, and can survive the fights when they come. I am also putting such perks as come my way into enchanting beacuse if I can't increase my weapons further, sooner or later I'll have to make my own.
Which brings me back to where I started, can one play at high levels without resorting to smithing/enchanting/magic or, maybe, alchemy?