With good knowledge of the game locations,items, and quests even master difficulty with PISE installed and practically zero use of trade skills ( smithing , enchanting , alchemy) the game can still be made relatively easy.
The game is too easy because it doesn't use oblivion's scaling system which quiet literally punishes you for unoptimized leveling. Add in the ridiculous power of the trade skills and you can break the game as soon as you have enough gold to buy a few hundred crafting materials.
Monster level scaling in skyrim is an absolute mess. Too often you will meet hordes of level 1 draugr even though youre well past the point where they would be a challenge or even nuisance. The reverse side is meeting draugr overlords when you're far too low. While i realize most people consider skyrim a "skilless" game i would argue there are some aspects, mostly game knowledge that can set causal players from seasoned players. While it is impossible to balance for both, master difficulty should present a challenge to the latter group. There needs to be a 5th difficulty mode called "masochist" mode that would only be playable if the player made the most out of their crafting skills, min-maxed the hell out of their stats, and planned every perk from level 1 to 50, and got real comfortable hitting that quickload button.
Outside of difficulty issues there is a massive imbalance between weapon damage and spell damage. As someone who has always loved playing the mage class in rpgs i was incredibly disheartened to see that a dull knife tends to do as much damage in the long run as a high powered spell. spells requires a massive investment in either enchantment slots or magicka stat which takes away from health. Weapon damage requires no perks in the weapon tree or any enchantments to reach ridiculous levels. There is absolutely no reason to cast destruction spells in skyrim outside of the flavor/rpg aspect because weapons can do the job better and without cost.
crafting skills do not ruin the game- you can still breeze through without them and you certainly have a choice in using them. some one else said it best, skyrim is balanced around first times players fumbling around and spending most of their perks in the speech or pickpocket tree. 14 hours in, level 19, master difficulty with PISE, almost zero trade skills and im already finding myself bored at the difficulty.